Structural features and photophysical behavior of carborane-appended BODIPY dyes

Structural features and photophysical behavior of carborane-appended BODIPY dyes | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Structural features and photophysical behavior of carborane-appended BODIPY dyes Swaraj Kumar Beriha, Chandra Sekhara Mahanta, Brundabana Naik, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6893909/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract A series of carborane-appended BODIPY derivatives (compounds 4 - 8 ) were synthesized and investigated to understand the influence of carborane substitution on molecular conformation, electronic structure, and fluorescence behavior. The compounds were prepared using established synthetic routes, including Sonogashira and Suzuki cross-coupling, followed by dipyrromethane-based BODIPY formation and carborane incorporation. Density functional theory (DFT) calculations at the B3LYP/6-31G(d,p) level with solvent effects modeled via CPCM revealed that ortho- and meta -carborane substitutions (compounds 5 and 6 ) led to nearly planar geometries and partial delocalization of the LUMO onto adjacent phenyl rings, yet showed lower fluorescence quantum yields due to efficient photoinduced electron transfer (PET). In contrast, control compound 4 and compound 8 exhibited larger dihedral angles that disrupted π-conjugation but retained higher quantum yields, attributed to reduced PET. UV-Vis absorption and fluorescence spectra showed minimal shifts across all derivatives, with similar HOMO-LUMO gaps (2.24-2.92 eV) and emission in the 663–667 nm range. The findings underscore the delicate interplay between molecular conformation and excited-state processes in determining fluorescence efficiency. Notably, the integration of boron-rich carborane clusters with optically active BODIPY scaffolds presents a promising strategy for dual-functional cancer theranostics, including boron neutron capture therapy (BNCT) and photodynamic therapy (PDT), by combining boron delivery with fluorescent imaging capabilities. BODIPY dyes Icosahedral carboranes Fluorescence quenching DFT calculations Cancer therapy Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Highlights Carborane substitution alters molecular geometry and orbital distribution, affecting π-conjugation and enabling photoinduced electron transfer (PET) induced quenching. Fluorescence efficiency is governed more by dihedral angles and PET effects than by conjugation extent. BODIPY-carborane hybrids are promising for dual cancer therapies, including boron neutron capture therapy (BNCT) and photodynamic therapy (PDT) 1 Introduction Boron-dipyrromethene (BODIPY) dyes represent a class of highly fluorescent compounds that have garnered considerable attention due to their excellent photophysical properties, chemical stability, and versatile structural modifiability. BODIPY-based fluorophores have become indispensable in applications ranging from bioimaging and sensing to materials science and photodynamic therapy. The core structure of BODIPY (boron-dipyrromethene) dyes consists of a dipyrromethene ligand coordinated to a boron difluoride (BF₂) unit, forming a highly conjugated and planar system that supports extensive electron delocalization. The central feature of this structure is a π-conjugated system extending across the two pyrrole rings and the methine bridge that connects them, giving rise to strong absorption in the visible region and efficient fluorescence (Fig. 1 ) [ 1 – 3 ]. In terms of formal charge distribution, the neutral BODIPY core does not carry an overall charge. However, within its resonance structures, charge separation and delocalization can be observed that help stabilize the system. The dipyrromethene unit is a bidentate ligand, donating lone pair electrons from the nitrogen atoms of the two pyrrole rings to the electron-deficient boron center. Boron, being trivalent and lacking a full octet, accepts a pair of electrons from each nitrogen atom, forming a four-coordinate, pseudo-tetrahedral boron center in BODIPY (Fig. 1 ) [ 2 , 3 ]. BODIPY dyes are widely recognized for their exceptional photophysical and chemical properties, which make them highly suitable for a range of fluorescence-based applications. These fluorophores typically exhibit high fluorescence quantum yields, contributing to their strong emission intensity and sensitivity. Their narrow emission bands and minimal Stokes shifts enable precise spectral resolution, minimizing spectral overlap and improving signal-to-noise ratios in multi-color imaging systems. In addition, BODIPY derivatives demonstrate remarkable photostability, allowing sustained excitation with minimal photobleaching-an essential feature for live-cell imaging and time-lapse fluorescence studies. Structurally, the dyes possess a neutral and lipophilic character, facilitating efficient membrane permeability and reducing non-specific interactions in biological environments. These features, combined with their excellent compatibility with aqueous and physiological conditions, underscore the utility of BODIPY dyes in diverse fields such as bioimaging, sensing, flow cytometry, and drug delivery [ 1 , 2 ]. This highly planar and rigid structure gives rise to the strong absorption and emission characteristics that are a hallmark of BODIPY dyes. Substituents can be introduced at various positions (typically 1, 3, 5, and 8) on the BODIPY core to tune the dye’s spectroscopic and solubility properties. The modular nature of the BODIPY core allows for a wide range of chemical modifications. Substitution at the meso position (carbon 8) typically affects fluorescence intensity and electronic distribution, while substitution at positions 3 and 5 can significantly red-shift the absorption/emission maxima. Extension of the π-conjugation or introduction of electron-donating/withdrawing groups has been widely employed to produce BODIPY derivatives with tailored optical properties for specific applications (Fig. 1 ) [ 1 ]. Carboranes are a class of polyhedral boron–carbon cluster compounds known for their unique three-dimensional geometry, chemical robustness, and electron-deficient bonding. Among these, icosahedral carboranes, especially the closo -C₂B₁₀H₁₂ family, are the most widely studied. These 12-vertex clusters feature two carbon atoms and ten boron atoms arranged in a highly symmetrical icosahedral geometry. The ortho- (1,2-), meta- (1,7-), and para- (1,12-) isomers are classified based on the positions of the two carbon atoms in the cage (Fig. 1 ) [ 4 ]. Icosahedral carboranes display three-dimensional aromaticity, which contributes to their exceptional thermal and oxidative stability. These characteristics, combined with their chemical inertness and lipophilicity, have led to their integration into a variety of fields including medicinal chemistry, materials science, synthetic chemistry and organometallic chemistry [ 5 – 9 ]. In recent years, icosahedral carboranes have attracted considerable interest as modulators of photophysical properties in conjugated organic and organometallic systems. Due to their electron-withdrawing nature and non-planar, sterically demanding structure, incorporation of carborane cages into π-conjugated molecules often leads to significant changes in absorption, emission, and quantum yield. The incorporation of icosahedral carborane clusters into π-conjugated systems has emerged as a powerful strategy for modulating photophysical properties. Owing to their electron-deficient nature, structural rigidity, and steric bulk, carboranes impart several notable effects on the optical behavior of organic and organometallic chromophores. Carborane units can induce either quenching or enhancement of fluorescence, depending on the mode of incorporation and the surrounding electronic environment. When directly conjugated to electron-donating groups, the carborane cage often acts as an electron-accepting moiety, facilitating intramolecular charge transfer (ICT). This charge separation can lead to tunable emission wavelengths, including red-shifted or dual-emissive behavior, depending on the strength of the donor–acceptor interaction and the solvent polarity [ 10 – 12 ]. The bulky and non-planar geometry of the icosahedral cluster effectively disrupts π–π stacking interactions in the solid state. This feature is particularly advantageous in mitigating aggregation-caused quenching (ACQ), a common limitation in planar luminophores. As a result, carborane-functionalized compounds frequently exhibit enhanced solid-state luminescence, which is beneficial for the development of robust emissive materials [ 13 ]. Carborane-containing donor–acceptor architectures can contribute to the stabilization of singlet and triplet excited states, thereby enabling the design of advanced emissive materials. In particular, such systems have shown promise in the development of thermally activated delayed fluorescence (TADF) and room-temperature phosphorescent (RTP) materials. The unique electronic features of the carborane cage help regulate energy gap alignment and suppress nonradiative decay, both of which are critical for efficient light emission in optoelectronic applications [ 14 ]. Collectively, these properties underscore the utility of icosahedral carboranes as functional elements for tuning photophysical behavior and advancing material performance in luminescent and photoactive systems. Carborane-appended BODIPY dyes are a class of luminescent materials that integrate the unique structural and electronic properties of carborane clusters with the exceptional fluorescence characteristics of BODIPY fluorophores. These conjugates have garnered significant attention for their potential applications in bioimaging, photodynamic therapy (PDT), and optoelectronic devices. The attachment of carborane clusters to BODIPY cores significantly influences their photophysical properties. Carborane substitution leads to red-shifted absorption and emission spectra, enhanced fluorescence quantum yields, and improved photostability. These modifications are attributed to the rigid geometry and 3D-aromaticity of carboranes, which facilitate extended π-conjugation and reduce non-radiative decay pathways. Additionally, the presence of carborane units can induce photoinduced electron transfer (PET) processes, as observed in ortho-carborane–BODIPY dyads, where PET efficiencies ranged from 63–71%, leading to fluorescence quenching and the generation of charge-separated states. Carborane-BODIPY conjugates are emerging as versatile materials with significant potential across various fields due to their unique photophysical properties and structural characteristics. In bioimaging, these conjugates offer superior fluorescence properties and enhanced cellular internalization, making them ideal candidates for in vitro cell tracking and imaging applications. In photodynamic therapy (PDT), they serve as potent photosensitizers capable of generating reactive oxygen species (ROS) upon light activation, thereby offering targeted cancer treatment options. Their high boron content also enhances their suitability as boron carriers for Boron Neutron Capture Therapy (BNCT). This cancer treatment modality relies on the capture of thermal neutrons by boron atoms. Furthermore, their tunable electronic properties and stability render them suitable for applications in optoelectronics, including organic light-emitting diodes (OLEDs) and sensors. Collectively, these attributes position carborane-BODIPY conjugates as valuable candidates for future research and development in both material and medicinal sciences [ 15 – 18 ]. A recent study by Mahanta et al. (2024) presents the design, synthesis, and anticancer evaluation of a series of carborane-BODIPY conjugates, highlighting their potential as effective anticancer agents. The study focuses on the synthesis of control BODIPY 4 and four carboranyl-BODIPY conjugates ortho - 5 , meta - 6 , compounds 7 and 8 (Fig. 2 ). In compounds 5 and 6 , ortho - and meta -carborane clusters are directly attached to the phenylene ring, which is covalently linked to the BODIPY fluorophore. Compounds 7 and 8 feature one and two ortho -carborane clusters, respectively, attached to the phenylene ring via an -O-CH₂- linkage, which is covalently bonded to the BODIPY fluorophore. In vitro cytotoxicity assessments against the HeLa cervical cancer cell line revealed that the ortho - 5 exhibited the highest cell death potential at lower concentrations (12.03 µM) and inhibited cell proliferation and migration. Flow cytometry studies indicated that ortho - 5 and compound 7 arrested the cell cycle at the S phase. These findings suggest that the carboranyl-BODIPY conjugates possess significant potential as effective anticancer agents [ 19 ]. In the present study, a detailed computational investigation of carborane-appended BODIPYs (Fig. 2 ) was conducted using Gaussian 09 to understand their structure and their photophysical properties have also been assessed. Density Functional Theory (DFT) calculations at the B3LYP/6-31G(d,p) level, including solvent effects via the polarizable continuum model (PCM), were used to optimize molecular geometries. The results showed that carborane substitution did not significantly distort the planarity of the BODIPY core, although slight steric effects were observed depending on the attachment site. Frontier molecular orbital (FMO) analysis revealed that the HOMO and LUMO were primarily localized on the BODIPY moiety, indicating limited electronic delocalization with the carborane unit. The compounds' absorption and emission maxima, along with their quantum yields, have also been measured. The study concluded that carboranyl substitution offers structural and photophysical tunability without compromising the fluorescence efficiency of the BODIPY core, supporting their potential application in bioimaging and cancer therapeutics. 2 Material and methods 2.1 Synthesis The synthesis of carborane-appended BODIPYs ( 4 – 8 ) has been previously reported, involving well-established methodologies such as Sonogashira and Suzuki cross-coupling reactions, decaborane insertion, and dipyrromethane-based BODIPY construction. These synthetic strategies typically include the formation of a dipyrromethane intermediate catalyzed by trifluoroacetic acid (TFA), followed by oxidation using DDQ to yield the corresponding dipyrromethene. Subsequent complexation with boron trifluoride diethyl etherate (BF₃·OEt₂) in the presence of a base like triethylamine (Et₃N) results in the formation of the fluorescent BODIPY core. Carborane units are then introduced through coupling or substitution reactions, enabling the creation of structurally diverse conjugates for functional studies in photophysics and biomedicine [ 19 ]. The structures of all synthesized conjugates were confirmed through a combination of FT-IR, NMR ( 1 H, 13 C, and 11 B), and high-resolution mass spectrometry (HRMS). 2.2 DFT calculations DFT calculations were performed using the Gaussian 09 suite of programs [ 20 ]. Full geometry optimizations were carried out at the B3LYP/6-31G (d,p) level of theory, incorporating solvent effects through the polarizable continuum model (CPCM) with dichloromethane as the solvent. For simplification, the ester groups of the BODIPYs have been replaced with methyl during the structure optimisation. 2.3 Photophysical properties UV-Vis absorption spectra were recorded using a Varian Cary 5000 UV-Vis-NIR spectrophotometer in spectroscopic grade solvents. Emission spectra were acquired at room temperature on a Varian Cary Eclipse fluorescence spectrometer, also using spectroscopic grade solvents. The fluorescence quantum yields of the carborane-appended BODIPY compounds ( 4 − 8) were determined by comparison with a standard fluorophore of known quantum yield, Rhodamine 6G, whose emission spectrum was recorded in dichloromethane. The emission spectra of the BODIPY derivatives were likewise measured in dichloromethane. Relative fluorescence quantum yields (Φ) were calculated by comparing the integrated emission intensities of the samples with that of Rhodamine 6G under identical experimental conditions [ 21 ]. Additionally, the HOMO–LUMO gap energies (optical band gaps) of the BODIPY derivatives were estimated and expressed in electron volts (eV) using the Planck equation, based on the wavelength at which the excitation and emission spectra intersect (λ c ) [ 22 ]. 3 Results and discussion 3.1 Optimized molecular structures The optimized molecular structures of the carborane-appended BODIPY derivatives were obtained using density functional theory (DFT) calculations carried out with the Gaussian 09 suite of programs [ 20 , 23 ]. Geometry optimizations were performed at the B3LYP/6-31G(d,p) level of theory, incorporating solvent effects via the polarizable continuum model (CPCM) using dichloromethane as the solvent. To simplify computational demands, the ester substituents on the BODIPY core were replaced with methyl groups. The resulting optimized structures revealed that the BODIPY core retained its characteristic planarity, while the carborane clusters, appended via alkynyl or aryl linkers, adopted orientations that minimized steric hindrance and electronic repulsion. Notably, the bulky carborane moieties were oriented nearly perpendicular to the BODIPY plane, consistent with their electronically insulating nature, thereby preserving the π-conjugation of the fluorophore. This structural arrangement supports the observed photophysical behavior, where minimal electronic communication between the carborane and BODIPY units helps retain high fluorescence quantum yields while imparting boron-rich characteristics (Figs. 3 and 4 ). The HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) represent the frontier orbitals that dictate a molecule’s chemical reactivity, photophysical behavior, and electronic properties. Following full geometry optimization using the Gaussian 09 suite, molecular orbital energies and spatial distributions were examined to evaluate electron delocalization across the molecular scaffold. Electron density visualizations revealed that, in the carborane-appended BODIPY derivatives 5 and 6 , the HOMO was predominantly localized on the electron-rich BODIPY core, while the LUMO extended over the BODIPY core and the adjacent phenyl ring. This suggests limited π-conjugation between the BODIPY framework and the carborane unit. In contrast, for the control compound 4 , both the HOMO and LUMO were strictly confined to the BODIPY core (Fig. 3 ). The HOMO–LUMO energy gap, a key indicator of the optical band gap and electronic transition energy, was calculated from the energy difference between the HOMO and LUMO as reported in the Gaussian 09 output. A smaller gap typically correlates with red-shifted absorption and enhanced delocalization, while a larger gap suggests localized electronic distributions and higher excitation energies. For compound 5 (with ortho -carborane directly attached to the phenyl ring), the HOMO and LUMO energies were found to be − 5.32 eV and − 3.01 eV, respectively, giving a gap of 2.31 eV. Similarly, for compound 6 ( meta -carborane substitution), the HOMO and LUMO energies were − 5.30 eV and − 2.99 eV, resulting in an identical gap of 2.31 eV (Fig. 3 ). However, for control 4 showed the HOMO and LUMO energies were found to be − 5.37 eV and − 2.45 eV, resulting in an identical gap of 2.92 eV. The dihedral angle-defined as the angle between two intersecting planes formed by four sequential atoms-provides insights into the molecular conformation and torsional flexibility. In compound 5 , the dihedral angle between the BODIPY core and the meso -aryl ring was found to be 1.09°, indicating a nearly coplanar arrangement. Additional dihedral angles were 34.98° (phenyl-phenyl) and 22.32° (phenyl- o -carborane). For compound 6 , the corresponding dihedral angles were 2.61° (BODIPY-aryl), 33.35° (phenyl-phenyl), and 19.85° (phenyl- m -carborane). These values suggest that both compounds share similar geometrical features, with near-planar orientation at the BODIPY core and modest torsional deviations near the carborane units. In the case of compound 4 , the dihedral angle between the BODIPY core and the adjacent phenyl ring was found to be nearly perpendicular at 87.28°, indicating a significant disruption of π-conjugation due to poor orbital overlap. Additionally, the dihedral angle between the central phenyl ring and the phenyl ring directly attached to the BODIPY core was 35.5°, while a similar angle of 36.26° was observed between the central phenyl ring and the terminal phenyl ring. These moderate torsional angles suggest partial conjugation along the phenyl linkage but confirm the electronic decoupling of the BODIPY core from the rest of the framework. The optimized structures of compounds 7 and 8 are shown in Fig. 4 . In compound 7 , where a single ortho -carborane unit is linked to the phenyl ring via an –OCH₂– bridge, the HOMO and LUMO energies were − 5.30 eV and − 2.89 eV, respectively, yielding a gap of 2.49 eV. In contrast, compound 8 , bearing two ortho -carborane moieties connected through –OCH₂– linkers, showed HOMO and LUMO energies of − 5.44 eV and − 2.53 eV, respectively, with a wider energy gap of 2.91 eV (Fig. 4 ). The trend in HOMO–LUMO gaps reflects how structural modifications influence the electronic delocalization and optical properties of the BODIPY framework. The electron density map of compound 7 shows that the HOMO is predominantly localized on the BODIPY core, while the LUMO extends across the BODIPY core and the adjacent phenyl ring, indicating partial delocalization. In contrast, for compound 8 , both the HOMO and LUMO remain largely confined to the BODIPY core, with minimal extension onto the phenyl ring. These observations suggest that the carborane units have limited influence on the frontier orbital distributions in both compounds. In compound 7 , the dihedral angle between the BODIPY core and the meso -aryl ring is 2.81°, indicating a nearly coplanar configuration, which promotes conjugation. Furthermore, the dihedral angle between the phenyl ring and the –OCH₂– linker (connecting the o -carborane moiety) is 0.062°, also reflecting a planar arrangement. In compound 8 , however, the dihedral angle between the BODIPY core and the meso -aryl ring is 95.98°, suggesting an orthogonal orientation. This implies that the phenyl ring is rotated nearly perpendicular to the BODIPY plane, effectively disrupting π-conjugation due to lack of orbital overlap. Meanwhile, the dihedral angle between the phenyl ring and the –OCH₂– linker (connecting the two o -carborane moieties) is 179.81°, indicating a near-planar geometry along that axis. 3.2. Photophysical properties The photophysical properties of the carborane-appended BODIPY derivatives and the control compound were investigated using UV–Vis and fluorescence spectroscopy in dichloromethane (see Fig. 5 and Table 1 ). All compounds exhibited similar absorption (λ max −abs ) and emission (λ max −em ) maxima, suggesting minimal influence from the carborane units on the electronic transitions. The absorption maxima for all samples were found to fall within the range of 538–540 nm. The emission spectra of the carborane-appended BODIPY derivatives and the control compound were recorded in dichloromethane. All compounds exhibited fluorescence in the 550–700 nm range, corresponding to the green-to-red region of the visible spectrum. The emission maxima were consistently observed between 663 and 667 nm, indicating that the incorporation of carborane clusters had minimal impact on the emission characteristics. Stokes shifts, calculated as the difference between excitation and emission maxima, ranged from 825 to 919 nm for all compounds (Table 1 ). Such low Stokes shifts typically indicate minimal geometric or electronic reorganization between the ground and excited states. This behavior is characteristic of rigid molecular structures with limited internal motion upon excitation. Additionally, small Stokes shifts suggest efficient orbital overlap between the HOMO and LUMO, leading to strong fluorescence where most of the excited-state energy is emitted as photons rather than lost through non-radiative decay pathways [ 15 , 22 – 27 ]. The HOMO-LUMO gap energies for both the control BODIPY compounds and the carborane-appended derivatives were estimated in electron volts (eV) using the Planck equation, based on the wavelength at which the excitation and emission spectra intersect (λ c ), as shown in Table 1 . All compounds exhibited similar gap energies, ranging from 2.24 to 2.25 eV. This consistency indicates that the incorporation of carborane units has a negligible effect on the optical band gap of the BODIPY core. The relative fluorescence quantum yields (Φ) of the control compound 4 and carborane-appended BODIPYs ( 5 – 8 ) were evaluated by comparing them to Rhodamine 6G, a standard fluorophore with a known quantum yield of 0.95. The quantum yields for the BODIPYs were determined by comparing the integrated areas under their emission spectra. The results, summarized in Table 1 , showed that BODIPY 8 , with two ortho -carborane moieties attached via -OCH₂- linkages, exhibited the highest quantum yield of 0.22, followed by the control compound 4 , which had a quantum yield of 0.18. The lowest quantum yield of 0.14 was observed for BODIPY 7 , which contained one ortho -carborane moiety attached via the same -OCH₂- linker. BODIPYs 6 and 7 , where ortho- and meta - carborane clusters were appended directly to the phenyl ring, showed moderate quantum yields of 0.15 and 0.18, respectively. Notably, the meta -carborane-substituted BODIPY 6 exhibited about 6% and 17% lower quantum yields compared to the control 4 . Overall, the attachment of carborane clusters to BODIPYs at different positions did not result in significant changes in quantum yield. This finding is consistent with the work of Bellomo et al ., who studied the photophysical behavior of carborane–BODIPY dyads. They showed that ortho -carborane substitution results in strong fluorescence quenching due to efficient photoinduced electron transfer (PET), driven by the close proximity between the carborane and BODIPY core, which promotes non-radiative decay and lower quantum yields. In contrast, meta -carborane substitution leads to weaker PET and better fluorescence efficiency, aligning with the results observed in the current study [ 15 ]. Table 1 Summary of photophysical properties of BODIPYs λ max −abs a (nm) λ max −em a (nm) Stokes shift (cm − 1 ) Optical Bandgap b (eV) Quantum Yield (Φ) c 4 538 566 919 2.25 0.18 5 539 567 916 2.25 0.15 6 538 566 919 2.25 0.17 7 538 563 825 2.25 0.14 8 540 566 850 2.24 0.22 a In dichloromethane solutions (1 × 10⁻⁵ M). b Band gap estimated the wavelength at which the excitation and emission spectra intersect (λ c ). 11 c Φ was calculated against Rhodamine 6G standard. 21 The dihedral angle between conjugated segments in BODIPY derivatives plays a critical role in modulating their quantum yields by influencing the extent of π-conjugation and electronic communication across the molecule. A small dihedral angle (close to planar geometry) facilitates effective orbital overlap, enhancing delocalization of the excited-state wave function and thereby increasing the radiative decay rate. In contrast, larger dihedral angles, especially those approaching orthogonality, disrupt π-conjugation, reduce oscillator strength, and can promote non-radiative decay pathways, ultimately lowering the fluorescence quantum yield. For example, BODIPY systems with sterically hindered substituents or rigid frameworks that enforce planarity often exhibit enhanced quantum yields due to improved electronic coupling and minimized internal conversion losses. This correlation between molecular conformation and emission efficiency is well-documented in the literature, particularly in studies investigating structure–property relationships in BODIPY dyes [ 2 ]. Although the dihedral angles in carborane-appended BODIPYs 5 and 6 were nearly planar-favoring better π-conjugation-significant fluorescence quenching was observed, attributed to efficient photoinduced electron transfer (PET), which reduced the quantum yield [ 15 ]. In contrast, despite the near-perpendicular dihedral angles in the control BODIPY 4 and BODIPY 8 , which disrupt π-conjugation, both compounds exhibited relatively higher quantum yields. This suggests that in the latter cases, the suppression of PET pathways plays a more dominant role in preserving fluorescence efficiency than extended conjugation. 4 Conclusion In this study, a series of carborane-appended BODIPY derivatives (compounds 4 – 8 ) were investigated through a combination of synthetic, computational, and photophysical approaches to elucidate the impact of carborane substitution on molecular geometry, electronic structure, and fluorescence behavior. DFT calculations at the B3LYP/6-31G(d,p) level revealed that compounds 5 and 6 , with ortho- and meta -carborane units directly attached to the phenyl ring, exhibited nearly planar geometries with partial frontier orbital delocalization onto the phenyl ring, yet showed reduced quantum yields due to efficient photoinduced electron transfer (PET). In contrast, control compound 4 and compound 8 , despite having large dihedral angles that disrupted π-conjugation, retained higher quantum yields, suggesting that suppression of PET pathways is a dominant factor in maintaining fluorescence efficiency. Optical band gap estimations and photophysical measurements confirmed that carborane incorporation had minimal effect on the absorption/emission maxima and HOMO-LUMO gaps, which remained largely governed by the BODIPY core. These findings align with previous reports that highlight the electronically insulating nature of carboranes and their potential role in modulating non-radiative decay processes rather than tuning spectral properties [ 2 , 15 , 24 , 25 ]. Importantly, the integration of boron-rich carborane clusters with fluorescent BODIPY frameworks presents a versatile platform for dual-functional cancer therapies. These conjugates hold promise for boron neutron capture therapy (BNCT), leveraging their high boron content, and for photodynamic therapy (PDT), due to their strong absorption and tunable fluorescence-enabling both therapeutic action and optical imaging guidance [ 24 – 27 ]. Declarations Acknowledgements BPD thanks Science & Engineering Research Board, India (grant number: CRG/2018/002635) and Odisha State Higher Education Council for the extramural research funding under MRIP-2023 (grant no. 23EM/CH/16). Author Contributions SKB synthesis, data collection and validation; CSM synthesis, data collection and validation; BN review and validation; PKS review and validation; NKS review and validation; RS synthesis and validation; DD review and validation, BPD conceptualization, data collection and validation, manuscript preparation and review. Data availability All data generated or analyzed during this study are included in this manuscript, and additional information is available from the corresponding author upon reasonable request. Ethics, Consent to Participate, and Consent to Publish Not applicable. Clinical trial Not applicable. Competing interests The authors declare no competing interests. References Ulrich, G.; Ziessel, R.; Harriman, A. The Chemistry of Fluorescent BODIPY Dyes: Versatility Unsurpassed. Angew. Chem. Int. Ed. 2008, 47 (7), 1184-1201. https://doi.org/10.1002/anie.200702070. Loudet, A.; Burgess, K. 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Liu, J.; Ma, Y.; Liu, Z.; et al. Enhancing Solid-State Luminescence through Carborane Incorporation. J. Am. Chem. Soc. 2018, 140 (15), 5526-5535. https://doi.org/10.1021/jacs.8b01942. Xie, Z.; Li, X.; Shi, W.; et al. Carborane-Modified Donor–Acceptor Systems for TADF Applications. Angew. Chem. Int. Ed. 2020, 59 (45), 19912-19918. https://doi.org/10.1002/anie.202008238. Bellomo, C.; Chaari, M.; Cabrera-González, J.; Blangetti, M.; Lombardi, C.; Deagostino, A.; Viñas, C.; Gaztelumendi, N.; Nogués, C.; Núñez, R.; Prandi, C. Carborane-BODIPY Dyads: New Photoluminescent Materials through an Efficient Heck Coupling. Chem.-Eur. J. 2018, 24 (58), 15622-15630. DOI: https://doi.org/10.1002/chem.201802901. Zaitsev, A. V.; Kiselev, S. S.; Smol'yakov, A. F.; Fedorov, Y. V.; Kononova, E. G.; Borisov, Y. A.; Ol'shevskaya, V. A. BODIPY Derivatives Modified with Carborane Clusters: Synthesis, Characterization and DFT Studies. Org. Biomol. Chem. 2023, 21 , 4084-4094. DOI: https://doi.org/10.1039/D3OB00255A. Jin, G. F.; Cho, Y.-J.; Wee, K.-R.; Hong, S. A.; Suh, I.-H.; Son, H.-J.; Lee, J.-D.; Han, W.-S.; Cho, D. W.; Kang, S. O. BODIPY Functionalized o-Carborane Dyads for Low-Energy Photosensitization. Dalton Trans. 2015, 44 (6), 2780-2787. DOI: https://doi.org/10.1039/c4dt03123g. Ordóñez-Hernández, L.; Planas, N.; Núñez, R. Carborane-Based BODIPY Dyes: Synthesis, Structural Analysis, Photophysics and Applications. Front. Chem. 2024, 12 , 1485301. DOI: https://doi.org/10.3389/fchem.2024.1485301. Mahanta, C. S.; Hansdah, S.; Khuntia, K.; Jena, B. B.; Swain, B. R.; Acharya, S.; Dash, B. P.; Debata, P. R.; Satapathy, R. Novel Carboranyl-BODIPY Conjugates: Design, Synthesis and Anti-Cancer Activity. RSC Adv. 2024, 14 (47), 34643-34660. https://doi.org/10.1039/D4RA07241C. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Petersson, G. A.; Nakatsuji, H.; et al. Gaussian 09 , Revision D.01; Gaussian, Inc.: Wallingford CT, 2013. Dash, B. P.; Hamilton, I.; Tate, D. J.; Crossley, D. L.; Kim, J. S.; Labram, J.; Anthopoulos, T. D.; Bronstein, H. Benzoselenadiazole and Benzotriazole Directed Electrophilic C–H Borylation of Conjugated Donor–Acceptor Materials. J. Mater. Chem. C 2019, 7 (30), 8993-9000. https://doi.org/10.1039/C9TC03055A. Lakowicz, J. R. Principles of Fluorescence Spectroscopy , 3rd ed.; Springer: New York, 2006. Madrid-Usuga, D.; Ortiz, A.; Reina, J. H . Photophysical Properties of BODIPY Derivatives for the Implementation of Organic Solar Cells: A Computational Approach . ACS Omega 2021, 6 (50), 34234-34242. DOI: https://doi.org/10.1021/acsomega.1c04598. Bellomo, E.; Trinh, T. B.; Brown, J. D.; Holten, D.; Bocian, D. F.; Lindsey, J. S. Photophysical Properties of Carborane-BODIPY Dyads: Insights into Excited-State Quenching Mechanisms . J. Org. Chem. 2016 , 81, 10715-10727. https://doi.org/10.1021/acs.joc.6b01752. Wang, J.; Guo, Y.; Xia, C.; Xu, X.; Zhang, Y.; Wu, Y. Suppressing Photoinduced Electron Transfer in Carborane-Based Fluorophores by Structural Tuning . J. Mater. Chem. C 2020 , 8, 4224-4232. https://doi.org/10.1039/D0TC00502D. Barth, R. F.; Coderre, J. A.; Vicente, M. G. H.; Blue, T. E . Boron Neutron Capture Therapy of Cancer: Current Status and Future Prospects . Clin. Cancer Res. 2005 , 11, 3987-4002. https://doi.org/10.1158/1078-0432.CCR-04-2629. Bonnet, S. Why Develop Photoactivated Chemotherapy? Dalton Trans. 2018 , 47, 10330-10343. https://doi.org/10.1039/C8DT01783K. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 21 Aug, 2025 Reviews received at journal 20 Aug, 2025 Reviews received at journal 22 Jul, 2025 Reviewers agreed at journal 21 Jul, 2025 Reviewers agreed at journal 16 Jul, 2025 Reviewers invited by journal 03 Jul, 2025 Editor assigned by journal 17 Jun, 2025 Submission checks completed at journal 17 Jun, 2025 First submitted to journal 14 Jun, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6893909","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":480214049,"identity":"e8163b32-4587-4ffb-9f60-401b56dfbb73","order_by":0,"name":"Swaraj Kumar Beriha","email":"","orcid":"","institution":"Siksha ‘O’ Anusandhan (Deemed to be University)","correspondingAuthor":false,"prefix":"","firstName":"Swaraj","middleName":"Kumar","lastName":"Beriha","suffix":""},{"id":480214050,"identity":"a610f981-f4c3-4146-98c2-a1778539c4de","order_by":1,"name":"Chandra Sekhara Mahanta","email":"","orcid":"","institution":"Ravenshaw University","correspondingAuthor":false,"prefix":"","firstName":"Chandra","middleName":"Sekhara","lastName":"Mahanta","suffix":""},{"id":480214051,"identity":"1008e9d7-6227-458c-994b-82488dde863c","order_by":2,"name":"Brundabana Naik","email":"","orcid":"","institution":"Siksha ‘O’ Anusandhan (Deemed to be University)","correspondingAuthor":false,"prefix":"","firstName":"Brundabana","middleName":"","lastName":"Naik","suffix":""},{"id":480214052,"identity":"bda0f4b2-e021-44ba-b3ec-cefed8889fe1","order_by":3,"name":"Prasanta Kumar Sahoo","email":"","orcid":"","institution":"National Institute of Hydrology","correspondingAuthor":false,"prefix":"","firstName":"Prasanta","middleName":"Kumar","lastName":"Sahoo","suffix":""},{"id":480214053,"identity":"569c480a-c19c-4ffd-a417-2a9581d1aaa1","order_by":4,"name":"Naresh Kumar Sahoo","email":"","orcid":"","institution":"Siksha ‘O’ Anusandhan (Deemed to be University)","correspondingAuthor":false,"prefix":"","firstName":"Naresh","middleName":"Kumar","lastName":"Sahoo","suffix":""},{"id":480214055,"identity":"cea7a477-8f7a-46e2-81bd-1df3142e3413","order_by":5,"name":"Rashmirekha Satapathy","email":"","orcid":"","institution":"Ravenshaw University","correspondingAuthor":false,"prefix":"","firstName":"Rashmirekha","middleName":"","lastName":"Satapathy","suffix":""},{"id":480214057,"identity":"8c365131-7f33-4c4e-b7ba-6748d8aad917","order_by":6,"name":"Debadutta Das","email":"","orcid":"","institution":"Buxi Jagabandhu Bidyadhar (Autonomous) College","correspondingAuthor":false,"prefix":"","firstName":"Debadutta","middleName":"","lastName":"Das","suffix":""},{"id":480214059,"identity":"0cfaf1cd-f6bd-4bfd-bb60-31cea7a03a45","order_by":7,"name":"Barada P. Dash","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA7ElEQVRIiWNgGAWjYBACAxDBw8DA2MDAw/gAxOYjRQsziMPDRooWNgkQh6AWc/azDz+8qWGQ7e8/e6zya46dDBsD88NHN/BosexJN5acc4zBeMaNvLTbstuSgQ5jMzbOweewA2kM0kBliQ03eMxuS25jBrJ52KTxajn/jPk3zz+GxPnnz5gVS26rJ0LLjTQ2ad42hsQNB3LMGD9uO0xYi+WMZ2yWc/skjDfeyDGWZtx2nIeNmYBfzPnTmG+8+WYjO+/8GcOPP7dV2/OzNz98jE8LFIBjhIGZB0wSVo4AjD9IUT0KRsEoGAUjBgAAFpFELXRAe/YAAAAASUVORK5CYII=","orcid":"","institution":"Rajdhani College","correspondingAuthor":true,"prefix":"","firstName":"Barada","middleName":"P.","lastName":"Dash","suffix":""}],"badges":[],"createdAt":"2025-06-14 12:23:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6893909/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6893909/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":86195908,"identity":"6a6c9ccf-46a8-462e-a51f-0cc0638f0e48","added_by":"auto","created_at":"2025-07-07 21:27:22","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":41326,"visible":true,"origin":"","legend":"\u003cp\u003eBODIPY core and IUPAC numbering, delocalized structures of BODIPY with formal charges and icosahedral carboranes.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6893909/v1/97ccb7c4ec08446a14cff4a7.png"},{"id":86195907,"identity":"6a24d53a-02d7-42d9-a74c-98ab7dbf7f1c","added_by":"auto","created_at":"2025-07-07 21:27:22","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":83318,"visible":true,"origin":"","legend":"\u003cp\u003eCarborane-appended BODIPY derivatives and the control.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6893909/v1/0dfbb8cb8c8e788353f5c1cd.png"},{"id":86196124,"identity":"fb86eed3-7a11-417f-b856-0ae0f6cd4282","added_by":"auto","created_at":"2025-07-07 21:35:22","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":313868,"visible":true,"origin":"","legend":"\u003cp\u003eOptimized ground-state structures, molecular orbital energy levels, and HOMO–LUMO molecular orbital contours (isovalue = 0.04) of carborane-appended BODIPYs: Compound \u003cstrong\u003e4 \u003c/strong\u003e(Control), Compound \u003cstrong\u003e5 \u003c/strong\u003e(\u003cem\u003eortho\u003c/em\u003e-carborane directly linked to the phenylene ring), and Compound \u003cstrong\u003e6\u003c/strong\u003e (\u003cem\u003emeta\u003c/em\u003e-carborane directly linked to the phenylene ring). Full geometry optimizations were performed at the B3LYP/6-31G(d,p) level using the Gaussian 09 suite, incorporating solvent effects via the CPCM model (dichloromethane). For computational simplicity, the ester substituents were replaced with methyl groups.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6893909/v1/523ddda0b0ab77eddea93687.png"},{"id":86195913,"identity":"bff75190-d437-4b07-aa36-2e81b809827f","added_by":"auto","created_at":"2025-07-07 21:27:22","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":216461,"visible":true,"origin":"","legend":"\u003cp\u003eOptimized ground-state structures, molecular orbital energy levels, and HOMO–LUMO molecular orbital contours (isovalue = 0.04) of carborane-appended BODIPY derivatives: Compound \u003cstrong\u003e7\u003c/strong\u003e (featuring one \u003cem\u003eortho\u003c/em\u003e-carborane moiety linked to the phenyl ring via an –OCH₂– bridge) and Compound \u003cstrong\u003e8\u003c/strong\u003e (bearing two \u003cem\u003eortho\u003c/em\u003e-carborane moieties attached to the phenyl ring through –OCH₂– linkers). Geometry optimizations were performed at the B3LYP/6-31G(d,p) level using the Gaussian 09 suite, with solvent effects included via the CPCM model (dichloromethane). For computational simplicity, ester groups were replaced with methyl substituents.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6893909/v1/b2117de8b2ca7624be34c715.png"},{"id":86196127,"identity":"929b6f78-7416-4c36-a70b-974b5cb33b76","added_by":"auto","created_at":"2025-07-07 21:35:22","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":124030,"visible":true,"origin":"","legend":"\u003cp\u003eNormalized absorption and fluorescence spectra of BODIPY (a) Control (\u003cstrong\u003e4\u003c/strong\u003e), (b) Ortho (\u003cstrong\u003e5\u003c/strong\u003e), (c) Meta (\u003cstrong\u003e6\u003c/strong\u003e), (d) Compound \u003cstrong\u003e7\u003c/strong\u003e (with one \u003cem\u003eo\u003c/em\u003e-carborane moiety attached via -OCH\u003csub\u003e2\u003c/sub\u003e- linkage), (e) Compound \u003cstrong\u003e8\u003c/strong\u003e (with two \u003cem\u003eo\u003c/em\u003e-carboarne moieties attached via -OCH\u003csub\u003e2\u003c/sub\u003e- linkages). UV and fluorescence spectra were recorded in dichloromethane solutions (1 × 10⁻⁵ M).\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6893909/v1/251e54e061d1be08b3eb7bcc.png"},{"id":86196443,"identity":"cdc4e247-3f64-4b20-9e80-bc462f665e74","added_by":"auto","created_at":"2025-07-07 21:43:22","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1332075,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6893909/v1/0591e198-12f1-44bb-95f2-e107af59b858.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Structural features and photophysical behavior of carborane-appended BODIPY dyes","fulltext":[{"header":"Highlights","content":"\u003cul\u003e\n \u003cli\u003eCarborane substitution alters molecular geometry and orbital distribution, affecting \u0026pi;-conjugation and enabling photoinduced electron transfer (PET) induced quenching.\u003c/li\u003e\n \u003cli\u003eFluorescence efficiency is governed more by dihedral angles and PET effects than by conjugation extent.\u003c/li\u003e\n \u003cli\u003eBODIPY-carborane hybrids are promising for dual cancer therapies, including boron neutron capture therapy (BNCT) and photodynamic therapy (PDT)\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"1 Introduction","content":"\u003cp\u003eBoron-dipyrromethene (BODIPY) dyes represent a class of highly fluorescent compounds that have garnered considerable attention due to their excellent photophysical properties, chemical stability, and versatile structural modifiability. BODIPY-based fluorophores have become indispensable in applications ranging from bioimaging and sensing to materials science and photodynamic therapy. The core structure of BODIPY (boron-dipyrromethene) dyes consists of a dipyrromethene ligand coordinated to a boron difluoride (BF₂) unit, forming a highly conjugated and planar system that supports extensive electron delocalization. The central feature of this structure is a π-conjugated system extending across the two pyrrole rings and the methine bridge that connects them, giving rise to strong absorption in the visible region and efficient fluorescence (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn terms of formal charge distribution, the neutral BODIPY core does not carry an overall charge. However, within its resonance structures, charge separation and delocalization can be observed that help stabilize the system. The dipyrromethene unit is a bidentate ligand, donating lone pair electrons from the nitrogen atoms of the two pyrrole rings to the electron-deficient boron center. Boron, being trivalent and lacking a full octet, accepts a pair of electrons from each nitrogen atom, forming a four-coordinate, pseudo-tetrahedral boron center in BODIPY (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eBODIPY dyes are widely recognized for their exceptional photophysical and chemical properties, which make them highly suitable for a range of fluorescence-based applications. These fluorophores typically exhibit high fluorescence quantum yields, contributing to their strong emission intensity and sensitivity. Their narrow emission bands and minimal Stokes shifts enable precise spectral resolution, minimizing spectral overlap and improving signal-to-noise ratios in multi-color imaging systems. In addition, BODIPY derivatives demonstrate remarkable photostability, allowing sustained excitation with minimal photobleaching-an essential feature for live-cell imaging and time-lapse fluorescence studies. Structurally, the dyes possess a neutral and lipophilic character, facilitating efficient membrane permeability and reducing non-specific interactions in biological environments. These features, combined with their excellent compatibility with aqueous and physiological conditions, underscore the utility of BODIPY dyes in diverse fields such as bioimaging, sensing, flow cytometry, and drug delivery [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThis highly planar and rigid structure gives rise to the strong absorption and emission characteristics that are a hallmark of BODIPY dyes. Substituents can be introduced at various positions (typically 1, 3, 5, and 8) on the BODIPY core to tune the dye\u0026rsquo;s spectroscopic and solubility properties. The modular nature of the BODIPY core allows for a wide range of chemical modifications. Substitution at the \u003cem\u003emeso\u003c/em\u003e position (carbon 8) typically affects fluorescence intensity and electronic distribution, while substitution at positions 3 and 5 can significantly red-shift the absorption/emission maxima. Extension of the π-conjugation or introduction of electron-donating/withdrawing groups has been widely employed to produce BODIPY derivatives with tailored optical properties for specific applications (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eCarboranes are a class of polyhedral boron\u0026ndash;carbon cluster compounds known for their unique three-dimensional geometry, chemical robustness, and electron-deficient bonding. Among these, icosahedral carboranes, especially the \u003cem\u003ecloso\u003c/em\u003e-C₂B₁₀H₁₂ family, are the most widely studied. These 12-vertex clusters feature two carbon atoms and ten boron atoms arranged in a highly symmetrical icosahedral geometry. The \u003cem\u003eortho-\u003c/em\u003e (1,2-), \u003cem\u003emeta-\u003c/em\u003e (1,7-), and \u003cem\u003epara-\u003c/em\u003e (1,12-) isomers are classified based on the positions of the two carbon atoms in the cage (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Icosahedral carboranes display three-dimensional aromaticity, which contributes to their exceptional thermal and oxidative stability. These characteristics, combined with their chemical inertness and lipophilicity, have led to their integration into a variety of fields including medicinal chemistry, materials science, synthetic chemistry and organometallic chemistry [\u003cspan additionalcitationids=\"CR6 CR7 CR8\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn recent years, icosahedral carboranes have attracted considerable interest as modulators of photophysical properties in conjugated organic and organometallic systems. Due to their electron-withdrawing nature and non-planar, sterically demanding structure, incorporation of carborane cages into π-conjugated molecules often leads to significant changes in absorption, emission, and quantum yield. The incorporation of icosahedral carborane clusters into π-conjugated systems has emerged as a powerful strategy for modulating photophysical properties. Owing to their electron-deficient nature, structural rigidity, and steric bulk, carboranes impart several notable effects on the optical behavior of organic and organometallic chromophores. Carborane units can induce either quenching or enhancement of fluorescence, depending on the mode of incorporation and the surrounding electronic environment. When directly conjugated to electron-donating groups, the carborane cage often acts as an electron-accepting moiety, facilitating intramolecular charge transfer (ICT). This charge separation can lead to tunable emission wavelengths, including red-shifted or dual-emissive behavior, depending on the strength of the donor\u0026ndash;acceptor interaction and the solvent polarity [\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. The bulky and non-planar geometry of the icosahedral cluster effectively disrupts π\u0026ndash;π stacking interactions in the solid state. This feature is particularly advantageous in mitigating aggregation-caused quenching (ACQ), a common limitation in planar luminophores. As a result, carborane-functionalized compounds frequently exhibit enhanced solid-state luminescence, which is beneficial for the development of robust emissive materials [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Carborane-containing donor\u0026ndash;acceptor architectures can contribute to the stabilization of singlet and triplet excited states, thereby enabling the design of advanced emissive materials. In particular, such systems have shown promise in the development of thermally activated delayed fluorescence (TADF) and room-temperature phosphorescent (RTP) materials. The unique electronic features of the carborane cage help regulate energy gap alignment and suppress nonradiative decay, both of which are critical for efficient light emission in optoelectronic applications [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Collectively, these properties underscore the utility of icosahedral carboranes as functional elements for tuning photophysical behavior and advancing material performance in luminescent and photoactive systems.\u003c/p\u003e\u003cp\u003eCarborane-appended BODIPY dyes are a class of luminescent materials that integrate the unique structural and electronic properties of carborane clusters with the exceptional fluorescence characteristics of BODIPY fluorophores. These conjugates have garnered significant attention for their potential applications in bioimaging, photodynamic therapy (PDT), and optoelectronic devices. The attachment of carborane clusters to BODIPY cores significantly influences their photophysical properties. Carborane substitution leads to red-shifted absorption and emission spectra, enhanced fluorescence quantum yields, and improved photostability. These modifications are attributed to the rigid geometry and 3D-aromaticity of carboranes, which facilitate extended π-conjugation and reduce non-radiative decay pathways. Additionally, the presence of carborane units can induce photoinduced electron transfer (PET) processes, as observed in ortho-carborane\u0026ndash;BODIPY dyads, where PET efficiencies ranged from 63\u0026ndash;71%, leading to fluorescence quenching and the generation of charge-separated states. Carborane-BODIPY conjugates are emerging as versatile materials with significant potential across various fields due to their unique photophysical properties and structural characteristics. In bioimaging, these conjugates offer superior fluorescence properties and enhanced cellular internalization, making them ideal candidates for in vitro cell tracking and imaging applications. In photodynamic therapy (PDT), they serve as potent photosensitizers capable of generating reactive oxygen species (ROS) upon light activation, thereby offering targeted cancer treatment options. Their high boron content also enhances their suitability as boron carriers for Boron Neutron Capture Therapy (BNCT). This cancer treatment modality relies on the capture of thermal neutrons by boron atoms. Furthermore, their tunable electronic properties and stability render them suitable for applications in optoelectronics, including organic light-emitting diodes (OLEDs) and sensors. Collectively, these attributes position carborane-BODIPY conjugates as valuable candidates for future research and development in both material and medicinal sciences [\u003cspan additionalcitationids=\"CR16 CR17\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. A recent study by Mahanta et al. (2024) presents the design, synthesis, and anticancer evaluation of a series of carborane-BODIPY conjugates, highlighting their potential as effective anticancer agents. The study focuses on the synthesis of control BODIPY \u003cb\u003e4\u003c/b\u003e and four carboranyl-BODIPY conjugates \u003cem\u003eortho\u003c/em\u003e-\u003cb\u003e5\u003c/b\u003e, \u003cem\u003emeta\u003c/em\u003e-\u003cb\u003e6\u003c/b\u003e, compounds \u003cb\u003e7\u003c/b\u003e and \u003cb\u003e8\u003c/b\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). In compounds \u003cb\u003e5\u003c/b\u003e and \u003cb\u003e6\u003c/b\u003e, \u003cem\u003eortho\u003c/em\u003e- and \u003cem\u003emeta\u003c/em\u003e-carborane clusters are directly attached to the phenylene ring, which is covalently linked to the BODIPY fluorophore. Compounds \u003cb\u003e7\u003c/b\u003e and \u003cb\u003e8\u003c/b\u003e feature one and two \u003cem\u003eortho\u003c/em\u003e-carborane clusters, respectively, attached to the phenylene ring via an -O-CH₂- linkage, which is covalently bonded to the BODIPY fluorophore. In vitro cytotoxicity assessments against the HeLa cervical cancer cell line revealed that the \u003cem\u003eortho\u003c/em\u003e-\u003cb\u003e5\u003c/b\u003e exhibited the highest cell death potential at lower concentrations (12.03 \u0026micro;M) and inhibited cell proliferation and migration. Flow cytometry studies indicated that \u003cem\u003eortho\u003c/em\u003e-\u003cb\u003e5\u003c/b\u003e and compound \u003cb\u003e7\u003c/b\u003e arrested the cell cycle at the S phase. These findings suggest that the carboranyl-BODIPY conjugates possess significant potential as effective anticancer agents [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn the present study, a detailed computational investigation of carborane-appended BODIPYs (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) was conducted using Gaussian 09 to understand their structure and their photophysical properties have also been assessed. Density Functional Theory (DFT) calculations at the B3LYP/6-31G(d,p) level, including solvent effects via the polarizable continuum model (PCM), were used to optimize molecular geometries. The results showed that carborane substitution did not significantly distort the planarity of the BODIPY core, although slight steric effects were observed depending on the attachment site. Frontier molecular orbital (FMO) analysis revealed that the HOMO and LUMO were primarily localized on the BODIPY moiety, indicating limited electronic delocalization with the carborane unit. The compounds' absorption and emission maxima, along with their quantum yields, have also been measured. The study concluded that carboranyl substitution offers structural and photophysical tunability without compromising the fluorescence efficiency of the BODIPY core, supporting their potential application in bioimaging and cancer therapeutics.\u003c/p\u003e"},{"header":"2 Material and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Synthesis\u003c/h2\u003e\u003cp\u003eThe synthesis of carborane-appended BODIPYs (\u003cb\u003e4\u003c/b\u003e\u0026ndash;\u003cb\u003e8\u003c/b\u003e) has been previously reported, involving well-established methodologies such as Sonogashira and Suzuki cross-coupling reactions, decaborane insertion, and dipyrromethane-based BODIPY construction. These synthetic strategies typically include the formation of a dipyrromethane intermediate catalyzed by trifluoroacetic acid (TFA), followed by oxidation using DDQ to yield the corresponding dipyrromethene. Subsequent complexation with boron trifluoride diethyl etherate (BF₃\u0026middot;OEt₂) in the presence of a base like triethylamine (Et₃N) results in the formation of the fluorescent BODIPY core. Carborane units are then introduced through coupling or substitution reactions, enabling the creation of structurally diverse conjugates for functional studies in photophysics and biomedicine [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The structures of all synthesized conjugates were confirmed through a combination of FT-IR, NMR (\u003csup\u003e1\u003c/sup\u003eH, \u003csup\u003e13\u003c/sup\u003eC, and \u003csup\u003e11\u003c/sup\u003eB), and high-resolution mass spectrometry (HRMS).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 DFT calculations\u003c/h2\u003e\u003cp\u003eDFT calculations were performed using the Gaussian 09 suite of programs [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Full geometry optimizations were carried out at the B3LYP/6-31G (d,p) level of theory, incorporating solvent effects through the polarizable continuum model (CPCM) with dichloromethane as the solvent. For simplification, the ester groups of the BODIPYs have been replaced with methyl during the structure optimisation.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Photophysical properties\u003c/h2\u003e\u003cp\u003eUV-Vis absorption spectra were recorded using a Varian Cary 5000 UV-Vis-NIR spectrophotometer in spectroscopic grade solvents. Emission spectra were acquired at room temperature on a Varian Cary Eclipse fluorescence spectrometer, also using spectroscopic grade solvents. The fluorescence quantum yields of the carborane-appended BODIPY compounds (\u003cb\u003e4\u003c/b\u003e \u0026minus;\u0026thinsp;8) were determined by comparison with a standard fluorophore of known quantum yield, Rhodamine 6G, whose emission spectrum was recorded in dichloromethane. The emission spectra of the BODIPY derivatives were likewise measured in dichloromethane. Relative fluorescence quantum yields (Φ) were calculated by comparing the integrated emission intensities of the samples with that of Rhodamine 6G under identical experimental conditions [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Additionally, the HOMO\u0026ndash;LUMO gap energies (optical band gaps) of the BODIPY derivatives were estimated and expressed in electron volts (eV) using the Planck equation, based on the wavelength at which the excitation and emission spectra intersect (λ\u003csub\u003ec\u003c/sub\u003e) [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e"},{"header":"3 Results and discussion","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Optimized molecular structures\u003c/h2\u003e\u003cp\u003eThe optimized molecular structures of the carborane-appended BODIPY derivatives were obtained using density functional theory (DFT) calculations carried out with the Gaussian 09 suite of programs [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Geometry optimizations were performed at the B3LYP/6-31G(d,p) level of theory, incorporating solvent effects via the polarizable continuum model (CPCM) using dichloromethane as the solvent. To simplify computational demands, the ester substituents on the BODIPY core were replaced with methyl groups. The resulting optimized structures revealed that the BODIPY core retained its characteristic planarity, while the carborane clusters, appended via alkynyl or aryl linkers, adopted orientations that minimized steric hindrance and electronic repulsion. Notably, the bulky carborane moieties were oriented nearly perpendicular to the BODIPY plane, consistent with their electronically insulating nature, thereby preserving the π-conjugation of the fluorophore. This structural arrangement supports the observed photophysical behavior, where minimal electronic communication between the carborane and BODIPY units helps retain high fluorescence quantum yields while imparting boron-rich characteristics (Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) represent the frontier orbitals that dictate a molecule\u0026rsquo;s chemical reactivity, photophysical behavior, and electronic properties. Following full geometry optimization using the Gaussian 09 suite, molecular orbital energies and spatial distributions were examined to evaluate electron delocalization across the molecular scaffold. Electron density visualizations revealed that, in the carborane-appended BODIPY derivatives \u003cb\u003e5\u003c/b\u003e and \u003cb\u003e6\u003c/b\u003e, the HOMO was predominantly localized on the electron-rich BODIPY core, while the LUMO extended over the BODIPY core and the adjacent phenyl ring. This suggests limited π-conjugation between the BODIPY framework and the carborane unit. In contrast, for the control compound \u003cb\u003e4\u003c/b\u003e, both the HOMO and LUMO were strictly confined to the BODIPY core (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe HOMO\u0026ndash;LUMO energy gap, a key indicator of the optical band gap and electronic transition energy, was calculated from the energy difference between the HOMO and LUMO as reported in the Gaussian 09 output. A smaller gap typically correlates with red-shifted absorption and enhanced delocalization, while a larger gap suggests localized electronic distributions and higher excitation energies. For compound \u003cb\u003e5\u003c/b\u003e (with \u003cem\u003eortho\u003c/em\u003e-carborane directly attached to the phenyl ring), the HOMO and LUMO energies were found to be \u0026minus;\u0026thinsp;5.32 eV and \u0026minus;\u0026thinsp;3.01 eV, respectively, giving a gap of 2.31 eV. Similarly, for compound \u003cb\u003e6\u003c/b\u003e (\u003cem\u003emeta\u003c/em\u003e-carborane substitution), the HOMO and LUMO energies were \u0026minus;\u0026thinsp;5.30 eV and \u0026minus;\u0026thinsp;2.99 eV, resulting in an identical gap of 2.31 eV (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eHowever, for control 4 showed the HOMO and LUMO energies were found to be \u0026minus;\u0026thinsp;5.37 eV and \u0026minus;\u0026thinsp;2.45 eV, resulting in an identical gap of 2.92 eV. The dihedral angle-defined as the angle between two intersecting planes formed by four sequential atoms-provides insights into the molecular conformation and torsional flexibility. In compound \u003cb\u003e5\u003c/b\u003e, the dihedral angle between the BODIPY core and the \u003cem\u003emeso\u003c/em\u003e-aryl ring was found to be 1.09\u0026deg;, indicating a nearly coplanar arrangement. Additional dihedral angles were 34.98\u0026deg; (phenyl-phenyl) and 22.32\u0026deg; (phenyl-\u003cem\u003eo\u003c/em\u003e-carborane). For compound \u003cb\u003e6\u003c/b\u003e, the corresponding dihedral angles were 2.61\u0026deg; (BODIPY-aryl), 33.35\u0026deg; (phenyl-phenyl), and 19.85\u0026deg; (phenyl-\u003cem\u003em\u003c/em\u003e-carborane). These values suggest that both compounds share similar geometrical features, with near-planar orientation at the BODIPY core and modest torsional deviations near the carborane units. In the case of compound \u003cb\u003e4\u003c/b\u003e, the dihedral angle between the BODIPY core and the adjacent phenyl ring was found to be nearly perpendicular at 87.28\u0026deg;, indicating a significant disruption of π-conjugation due to poor orbital overlap. Additionally, the dihedral angle between the central phenyl ring and the phenyl ring directly attached to the BODIPY core was 35.5\u0026deg;, while a similar angle of 36.26\u0026deg; was observed between the central phenyl ring and the terminal phenyl ring. These moderate torsional angles suggest partial conjugation along the phenyl linkage but confirm the electronic decoupling of the BODIPY core from the rest of the framework.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe optimized structures of compounds \u003cb\u003e7\u003c/b\u003e and \u003cb\u003e8\u003c/b\u003e are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. In compound \u003cb\u003e7\u003c/b\u003e, where a single \u003cem\u003eortho\u003c/em\u003e-carborane unit is linked to the phenyl ring via an \u0026ndash;OCH₂\u0026ndash; bridge, the HOMO and LUMO energies were \u0026minus;\u0026thinsp;5.30 eV and \u0026minus;\u0026thinsp;2.89 eV, respectively, yielding a gap of 2.49 eV. In contrast, compound \u003cb\u003e8\u003c/b\u003e, bearing two \u003cem\u003eortho\u003c/em\u003e-carborane moieties connected through \u0026ndash;OCH₂\u0026ndash; linkers, showed HOMO and LUMO energies of \u0026minus;\u0026thinsp;5.44 eV and \u0026minus;\u0026thinsp;2.53 eV, respectively, with a wider energy gap of 2.91 eV (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The trend in HOMO\u0026ndash;LUMO gaps reflects how structural modifications influence the electronic delocalization and optical properties of the BODIPY framework. The electron density map of compound \u003cb\u003e7\u003c/b\u003e shows that the HOMO is predominantly localized on the BODIPY core, while the LUMO extends across the BODIPY core and the adjacent phenyl ring, indicating partial delocalization. In contrast, for compound \u003cb\u003e8\u003c/b\u003e, both the HOMO and LUMO remain largely confined to the BODIPY core, with minimal extension onto the phenyl ring. These observations suggest that the carborane units have limited influence on the frontier orbital distributions in both compounds. In compound \u003cb\u003e7\u003c/b\u003e, the dihedral angle between the BODIPY core and the \u003cem\u003emeso\u003c/em\u003e-aryl ring is 2.81\u0026deg;, indicating a nearly coplanar configuration, which promotes conjugation. Furthermore, the dihedral angle between the phenyl ring and the \u0026ndash;OCH₂\u0026ndash; linker (connecting the \u003cem\u003eo\u003c/em\u003e-carborane moiety) is 0.062\u0026deg;, also reflecting a planar arrangement. In compound \u003cb\u003e8\u003c/b\u003e, however, the dihedral angle between the BODIPY core and the \u003cem\u003emeso\u003c/em\u003e-aryl ring is 95.98\u0026deg;, suggesting an orthogonal orientation. This implies that the phenyl ring is rotated nearly perpendicular to the BODIPY plane, effectively disrupting π-conjugation due to lack of orbital overlap. Meanwhile, the dihedral angle between the phenyl ring and the \u0026ndash;OCH₂\u0026ndash; linker (connecting the two \u003cem\u003eo\u003c/em\u003e-carborane moieties) is 179.81\u0026deg;, indicating a near-planar geometry along that axis.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Photophysical properties\u003c/h2\u003e\u003cp\u003eThe photophysical properties of the carborane-appended BODIPY derivatives and the control compound were investigated using UV\u0026ndash;Vis and fluorescence spectroscopy in dichloromethane (see Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e and Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). All compounds exhibited similar absorption (λ\u003csub\u003emax \u0026minus;abs\u003c/sub\u003e) and emission (λ\u003csub\u003emax \u0026minus;em\u003c/sub\u003e) maxima, suggesting minimal influence from the carborane units on the electronic transitions. The absorption maxima for all samples were found to fall within the range of 538\u0026ndash;540 nm. The emission spectra of the carborane-appended BODIPY derivatives and the control compound were recorded in dichloromethane. All compounds exhibited fluorescence in the 550\u0026ndash;700 nm range, corresponding to the green-to-red region of the visible spectrum. The emission maxima were consistently observed between 663 and 667 nm, indicating that the incorporation of carborane clusters had minimal impact on the emission characteristics.\u003c/p\u003e\u003cp\u003eStokes shifts, calculated as the difference between excitation and emission maxima, ranged from 825 to 919 nm for all compounds (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Such low Stokes shifts typically indicate minimal geometric or electronic reorganization between the ground and excited states. This behavior is characteristic of rigid molecular structures with limited internal motion upon excitation. Additionally, small Stokes shifts suggest efficient orbital overlap between the HOMO and LUMO, leading to strong fluorescence where most of the excited-state energy is emitted as photons rather than lost through non-radiative decay pathways [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan additionalcitationids=\"CR23 CR24 CR25 CR26\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe HOMO-LUMO gap energies for both the control BODIPY compounds and the carborane-appended derivatives were estimated in electron volts (eV) using the Planck equation, based on the wavelength at which the excitation and emission spectra intersect (λ\u003csub\u003ec\u003c/sub\u003e), as shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. All compounds exhibited similar gap energies, ranging from 2.24 to 2.25 eV. This consistency indicates that the incorporation of carborane units has a negligible effect on the optical band gap of the BODIPY core.\u003c/p\u003e\u003cp\u003eThe relative fluorescence quantum yields (Φ) of the control compound \u003cb\u003e4\u003c/b\u003e and carborane-appended BODIPYs (\u003cb\u003e5\u003c/b\u003e\u0026ndash;\u003cb\u003e8\u003c/b\u003e) were evaluated by comparing them to Rhodamine 6G, a standard fluorophore with a known quantum yield of 0.95. The quantum yields for the BODIPYs were determined by comparing the integrated areas under their emission spectra. The results, summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, showed that BODIPY \u003cb\u003e8\u003c/b\u003e, with two \u003cem\u003eortho\u003c/em\u003e-carborane moieties attached via -OCH₂- linkages, exhibited the highest quantum yield of 0.22, followed by the control compound \u003cb\u003e4\u003c/b\u003e, which had a quantum yield of 0.18. The lowest quantum yield of 0.14 was observed for BODIPY \u003cb\u003e7\u003c/b\u003e, which contained one \u003cem\u003eortho\u003c/em\u003e-carborane moiety attached via the same -OCH₂- linker. BODIPYs \u003cb\u003e6\u003c/b\u003e and \u003cb\u003e7\u003c/b\u003e, where \u003cem\u003eortho-\u003c/em\u003e and \u003cem\u003emeta\u003c/em\u003e\u003cb\u003e-\u003c/b\u003ecarborane clusters were appended directly to the phenyl ring, showed moderate quantum yields of 0.15 and 0.18, respectively. Notably, the \u003cem\u003emeta\u003c/em\u003e-carborane-substituted BODIPY \u003cb\u003e6\u003c/b\u003e exhibited about \u003cb\u003e6%\u003c/b\u003e and \u003cb\u003e17%\u003c/b\u003e lower quantum yields compared to the control \u003cb\u003e4\u003c/b\u003e. Overall, the attachment of carborane clusters to BODIPYs at different positions did not result in significant changes in quantum yield. This finding is consistent with the work of Bellomo \u003cem\u003eet al\u003c/em\u003e., who studied the photophysical behavior of carborane\u0026ndash;BODIPY dyads. They showed that \u003cem\u003eortho\u003c/em\u003e-carborane substitution results in strong fluorescence quenching due to efficient photoinduced electron transfer (PET), driven by the close proximity between the carborane and BODIPY core, which promotes non-radiative decay and lower quantum yields. In contrast, \u003cem\u003emeta\u003c/em\u003e-carborane substitution leads to weaker PET and better fluorescence efficiency, aligning with the results observed in the current study [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSummary of photophysical properties of BODIPYs\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eλ\u003csub\u003emax \u0026minus;abs\u003c/sub\u003e\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(nm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eλ\u003csub\u003emax \u0026minus;em\u003c/sub\u003e\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(nm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eStokes shift (cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eOptical Bandgap\u003csup\u003eb\u003c/sup\u003e (eV)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eQuantum Yield (Φ)\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e538\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e566\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e919\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e2.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.18\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e539\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e567\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e916\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e2.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e538\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e566\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e919\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e2.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.17\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e538\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e563\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e825\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e2.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.14\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e540\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e566\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e850\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e2.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.22\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"6\"\u003e\u003csup\u003ea\u003c/sup\u003e In dichloromethane solutions (1 \u0026times; 10⁻⁵ M). \u003csup\u003eb\u003c/sup\u003eBand gap estimated the wavelength at which the excitation and emission spectra intersect (λ\u003csub\u003ec\u003c/sub\u003e).\u003csup\u003e11 c\u003c/sup\u003eΦ was calculated against Rhodamine 6G standard.\u003csup\u003e21\u003c/sup\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe dihedral angle between conjugated segments in BODIPY derivatives plays a critical role in modulating their quantum yields by influencing the extent of π-conjugation and electronic communication across the molecule. A small dihedral angle (close to planar geometry) facilitates effective orbital overlap, enhancing delocalization of the excited-state wave function and thereby increasing the radiative decay rate. In contrast, larger dihedral angles, especially those approaching orthogonality, disrupt π-conjugation, reduce oscillator strength, and can promote non-radiative decay pathways, ultimately lowering the fluorescence quantum yield. For example, BODIPY systems with sterically hindered substituents or rigid frameworks that enforce planarity often exhibit enhanced quantum yields due to improved electronic coupling and minimized internal conversion losses. This correlation between molecular conformation and emission efficiency is well-documented in the literature, particularly in studies investigating structure\u0026ndash;property relationships in BODIPY dyes [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Although the dihedral angles in carborane-appended BODIPYs \u003cb\u003e5\u003c/b\u003e and \u003cb\u003e6\u003c/b\u003e were nearly planar-favoring better π-conjugation-significant fluorescence quenching was observed, attributed to efficient photoinduced electron transfer (PET), which reduced the quantum yield [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. In contrast, despite the near-perpendicular dihedral angles in the control BODIPY \u003cb\u003e4\u003c/b\u003e and BODIPY \u003cb\u003e8\u003c/b\u003e, which disrupt π-conjugation, both compounds exhibited relatively higher quantum yields. This suggests that in the latter cases, the suppression of PET pathways plays a more dominant role in preserving fluorescence efficiency than extended conjugation.\u003c/p\u003e\u003c/div\u003e"},{"header":"4 Conclusion","content":"\u003cp\u003eIn this study, a series of carborane-appended BODIPY derivatives (compounds \u003cb\u003e4\u003c/b\u003e\u0026ndash;\u003cb\u003e8\u003c/b\u003e) were investigated through a combination of synthetic, computational, and photophysical approaches to elucidate the impact of carborane substitution on molecular geometry, electronic structure, and fluorescence behavior. DFT calculations at the B3LYP/6-31G(d,p) level revealed that compounds \u003cb\u003e5\u003c/b\u003e and \u003cb\u003e6\u003c/b\u003e, with \u003cem\u003eortho-\u003c/em\u003e and \u003cem\u003emeta\u003c/em\u003e-carborane units directly attached to the phenyl ring, exhibited nearly planar geometries with partial frontier orbital delocalization onto the phenyl ring, yet showed reduced quantum yields due to efficient photoinduced electron transfer (PET). In contrast, control compound \u003cb\u003e4\u003c/b\u003e and compound \u003cb\u003e8\u003c/b\u003e, despite having large dihedral angles that disrupted π-conjugation, retained higher quantum yields, suggesting that suppression of PET pathways is a dominant factor in maintaining fluorescence efficiency. Optical band gap estimations and photophysical measurements confirmed that carborane incorporation had minimal effect on the absorption/emission maxima and HOMO-LUMO gaps, which remained largely governed by the BODIPY core. These findings align with previous reports that highlight the electronically insulating nature of carboranes and their potential role in modulating non-radiative decay processes rather than tuning spectral properties [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Importantly, the integration of boron-rich carborane clusters with fluorescent BODIPY frameworks presents a versatile platform for dual-functional cancer therapies. These conjugates hold promise for boron neutron capture therapy (BNCT), leveraging their high boron content, and for photodynamic therapy (PDT), due to their strong absorption and tunable fluorescence-enabling both therapeutic action and optical imaging guidance [\u003cspan additionalcitationids=\"CR25 CR26\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e BPD thanks Science \u0026amp; Engineering Research Board, India (grant number: CRG/2018/002635) and Odisha State Higher Education Council for the extramural research funding under MRIP-2023 (grant no. 23EM/CH/16).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e SKB synthesis, data collection and validation; CSM synthesis, data collection and validation; BN review and validation; PKS review and validation; NKS review and validation; RS synthesis and validation; DD review and validation, BPD conceptualization, data collection and validation, manuscript preparation and review.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e All data generated or analyzed during this study are included in this manuscript, and additional information is available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics, Consent to Participate, and Consent to Publish\u003c/strong\u003e Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial\u003c/strong\u003e Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e The authors declare no competing interests.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eUlrich, G.; Ziessel, R.; Harriman, A. 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R. \u003cem\u003ePrinciples of Fluorescence Spectroscopy\u003c/em\u003e\u003cem\u003e,\u003c/em\u003e 3rd ed.; Springer: New York, 2006.\u003c/li\u003e\n \u003cli\u003eMadrid-Usuga, D.; Ortiz, A.; Reina, J. H\u003cem\u003e. \u003cem\u003ePhotophysical Properties of BODIPY Derivatives for the Implementation of Organic Solar Cells: A Computational Approach\u003c/em\u003e. \u003cem\u003eACS Omega\u003c/em\u003e\u003c/em\u003e 2021, \u003cem\u003e6\u003c/em\u003e (50), 34234-34242. DOI: https://doi.org/10.1021/acsomega.1c04598.\u003c/li\u003e\n \u003cli\u003eBellomo, E.; Trinh, T. B.; Brown, J. D.; Holten, D.; Bocian, D. F.; Lindsey, J. S. \u003cem\u003ePhotophysical Properties of Carborane-BODIPY Dyads: Insights into Excited-State Quenching Mechanisms\u003c/em\u003e\u003cem\u003e.\u003c/em\u003e J. Org. Chem. \u003cem\u003e2016\u003c/em\u003e, 81, 10715-10727. https://doi.org/10.1021/acs.joc.6b01752.\u003c/li\u003e\n \u003cli\u003eWang, J.; Guo, Y.; Xia, C.; Xu, X.; Zhang, Y.; Wu, Y. \u003cem\u003eSuppressing Photoinduced Electron Transfer in Carborane-Based Fluorophores by Structural Tuning\u003c/em\u003e\u003cem\u003e.\u003c/em\u003e J. Mater. Chem. C \u003cem\u003e2020\u003c/em\u003e, 8, 4224-4232. https://doi.org/10.1039/D0TC00502D. \u003c/li\u003e\n \u003cli\u003eBarth, R. F.; Coderre, J. A.; Vicente, M. G. H.; Blue, T. E\u003cem\u003e. \u003cem\u003eBoron Neutron Capture Therapy of Cancer: Current Status and Future Prospects\u003c/em\u003e.\u003c/em\u003e Clin. Cancer Res. \u003cem\u003e2005\u003c/em\u003e, 11, 3987-4002. https://doi.org/10.1158/1078-0432.CCR-04-2629.\u003c/li\u003e\n \u003cli\u003eBonnet, S. \u003cem\u003eWhy Develop Photoactivated Chemotherapy?\u003c/em\u003e Dalton Trans. \u003cem\u003e2018\u003c/em\u003e, 47, 10330-10343. https://doi.org/10.1039/C8DT01783K. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-applied-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Applied Sciences](https://link.springer.com/journal/42452)","snPcode":"42452","submissionUrl":"https://submission.springernature.com/new-submission/42452/3","title":"Discover Applied Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"BODIPY dyes, Icosahedral carboranes, Fluorescence quenching, DFT calculations, Cancer therapy","lastPublishedDoi":"10.21203/rs.3.rs-6893909/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6893909/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eA series of carborane-appended BODIPY derivatives (compounds \u003cstrong\u003e4\u003c/strong\u003e-\u003cstrong\u003e8\u003c/strong\u003e) were synthesized and investigated to understand the influence of carborane substitution on molecular conformation, electronic structure, and fluorescence behavior. The compounds were prepared using established synthetic routes, including Sonogashira and Suzuki cross-coupling, followed by dipyrromethane-based BODIPY formation and carborane incorporation. Density functional theory (DFT) calculations at the B3LYP/6-31G(d,p) level with solvent effects modeled via CPCM revealed that \u003cem\u003eortho-\u003c/em\u003e and \u003cem\u003emeta\u003c/em\u003e-carborane substitutions (compounds \u003cstrong\u003e5\u003c/strong\u003e and \u003cstrong\u003e6\u003c/strong\u003e) led to nearly planar geometries and partial delocalization of the LUMO onto adjacent phenyl rings, yet showed lower fluorescence quantum yields due to efficient photoinduced electron transfer (PET). In contrast, control compound \u003cstrong\u003e4\u003c/strong\u003e and compound \u003cstrong\u003e8\u003c/strong\u003e exhibited larger dihedral angles that disrupted π-conjugation but retained higher quantum yields, attributed to reduced PET. UV-Vis absorption and fluorescence spectra showed minimal shifts across all derivatives, with similar HOMO-LUMO gaps (2.24-2.92 eV) and emission in the 663–667 nm range. The findings underscore the delicate interplay between molecular conformation and excited-state processes in determining fluorescence efficiency. Notably, the integration of boron-rich carborane clusters with optically active BODIPY scaffolds presents a promising strategy for dual-functional cancer theranostics, including boron neutron capture therapy (BNCT) and photodynamic therapy (PDT), by combining boron delivery with fluorescent imaging capabilities.\u003c/p\u003e","manuscriptTitle":"Structural features and photophysical behavior of carborane-appended BODIPY dyes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-07 21:27:17","doi":"10.21203/rs.3.rs-6893909/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-08-21T12:58:19+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-20T14:31:11+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-22T04:52:33+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"173125542522043432902485572837531715423","date":"2025-07-21T10:08:50+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"264714658046206734333019834439009100151","date":"2025-07-16T09:15:14+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-03T13:16:11+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-17T09:10:00+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-17T09:06:31+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Applied Sciences","date":"2025-06-14T12:13:42+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-applied-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Applied Sciences](https://link.springer.com/journal/42452)","snPcode":"42452","submissionUrl":"https://submission.springernature.com/new-submission/42452/3","title":"Discover Applied Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"14c8010f-36e7-466c-8f31-d593d6ee1f2d","owner":[],"postedDate":"July 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-10-16T19:08:24+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-07 21:27:17","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6893909","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6893909","identity":"rs-6893909","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}