DFT and TDDFT Based Investigation of Electronic Structure and Spectral Properties of a Triazole Thiophene Molecule

DFT and TDDFT Based Investigation of Electronic Structure and Spectral Properties of a Triazole Thiophene Molecule | 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 DFT and TDDFT Based Investigation of Electronic Structure and Spectral Properties of a Triazole Thiophene Molecule Mehmet Hanifi Kebiroglu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7067223/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This work delivers a rigorous density-functional investigation of 5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA). Hybrid-functional DFT calculations yield a near-planar, π-conjugated geometry and a HOMO–LUMO gap of ~ 3.1 eV, confirming the molecule’s electronic stability and photoactivity. Simulated FT-IR, NMR, and UV–Vis spectra reproduce key experimental fingerprints, with broad π→π* and n→π* absorptions underscoring optoelectronic promise. DOS and OPDOS profiles reveal efficient charge transfer across the triazole–thiophene scaffold, while electrostatic-potential mapping pinpoints electrophilic and nucleophilic sites relevant to metal coordination and molecular recognition. Reduced-density-gradient analysis visualizes weak intermolecular forces that may facilitate supramolecular assembly. These insights position TTCA as a versatile candidate for sensor platforms, coordination complexes, and bioactive materials, and they outline clear avenues for future optimization and application. TTCA Quantum Chemical Calculations DFT MEP NMR FT-IR Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Introduction Heteroaromatic scaffolds 1,2,4-triazole and thiophene cores occupy a privileged position in drug discovery and materials chemistry owing to their high hetero-atom density and pronounced electronic delocalization [ 1 ]. Triazole rings constitute the structural backbone of first-line systemic antifungal agents (e.g., fluconazole, voriconazole); systematic structure activity-relationship studies continue to produce novel triazole analogues with broader activity spectra and reduced resistance liabilities [ 2 ]. Conversely, suitably substituted thiophene esters have been shown to trigger intrinsic apoptotic pathways in hematological and solid-tumor cell lines, underscoring the thiophene scaffold as a potent anticancer motif [ 3 ]. Fusing these two heterocycles within a single molecule therefore represents a rational strategy for developing bifunctional agents capable of exerting simultaneous antifungal and anticancer activities [ 4 ]. Beyond pharmacology, the triazole–thiophene dyad is highly attractive for sensor technology: its conjugated backbone and electron-rich hetero-atoms facilitate charge-transfer processes that translate molecular recognition events into optical or electrochemical signals [ 5 , 6 ]. Carboxylic-acid functionalization further enhances this versatility; triazole polycarboxylates act as robust multidentate ligands that assemble metal-organic frameworks or coordination polymers combining permanent porosity with stimulus-responsive luminescence. Combining these attributes in a compact, synthetically accessible scaffold, 5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA) emerges as a compelling candidate for both drug design and sensor architectures. Nonetheless, no comprehensive theoretical study has yet correlated TTCA’s electronic structure with its prospective biological activity, sensor performance, or ligand behavior [ 7 ]. The present work addresses this gap by providing the first detailed DFT investigation of TTCA including geometry optimization, electronic distribution, spectroscopic fingerprints, and non-covalent interaction profile thereby furnishing insights that can guide future synthesis, coordination-chemistry design, and triazole-thiophene-based sensor development. To ensure that our theoretical predictions achieve the highest attainable accuracy, we adopted advanced first-principles approaches, with particular emphasis on hybrid-functional DFT calculations validated by time-dependent extensions where appropriate. In doing so, we not only establish a reliable description of TTCA but also identify knowledge gaps and propose concrete avenues for future studies aimed at property optimization, functional derivatization and device-level integration. These considerations underscore the broader relevance of TTCA and frame the present contribution as both a definitive characterization and a springboard for downstream applications. Methods 5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA) was modeled in Gaussian 09 with the hybrid B3LYP functional and the 6-311 + + G(d,p) basis set. The neutral singlet species was subjected to full geometry optimization under “tight” convergence criteria and an ultrafine integration grid to secure numerical accuracy [ 8 ]. A subsequent harmonic-frequency calculation confirmed the absence of imaginary modes, verifying that the structure corresponds to a true potential-energy minimum. Frontier-orbital energies (HOMO–LUMO) with the global reactivity descriptors were extracted from single-point calculations at the optimized geometry [ 9 ]. Total and fragment-resolved density-of-states (DOS) Total density of states (TDOS) and overlap-population density of states (OPDOS) profiles were obtained by processing the B3LYP molecular-orbital energies in GaussSum 3.0 with a Gaussian broadening of 0.30 eV, allowing the electronic contributions of the triazole, thiophene, and carboxylate fragments to be distinguished [ 10 ]. The molecular electrostatic potential (MEP) was mapped on the 0.001 a.u. electron-density isosurface using Multiwfn 3.8 and rendered in VMD 1.9.4. Non-covalent interaction (NCI) regions were characterized with the reduced-density-gradient (RDG) approach implemented in Multiwfn, revealing hydrogen bonds, van der Waals contacts, and steric effects pertinent to molecular recognition. Optical properties were evaluated by time-dependent DFT (TD-B3LYP/6-311 + + G(d,p)) including the first 20 singlet excited states. Vertical excitation energies and oscillator strengths were convoluted with a 0.10 eV Lorentzian to generate the simulated UV–Vis absorption spectrum. For vibrational benchmarking, theoretical FT-IR intensities obtained from the harmonic analysis were scaled by a factor of 0.967 and directly compared with literature data for structurally related heterocycles [ 11 – 13 ]. This integrated protocol delivers a self-consistent description of TTCA’s equilibrium geometry, electronic structure, vibrational stability, and photophysical behavior, thereby providing a robust computational foundation for subsequent structure property analyses [ 14 – 16 ] (Hassan et al., 2023; Tharuman et al., 2025; Lan et al., 2019). Results and Discussion Geometry Optimization The geometric structure of the 5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA) molecule was optimized using the Density Functional Theory (DFT) method implemented in the Gaussian software package. The optimized structure of the 5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA) molecule is presented in Fig. 1 . The optimized molecular structure in Fig. 1 reveals the planarity of the TTCA molecule and its potential for intramolecular interactions. Some observed that the triazole and thiophene rings lie almost within the same plane, indicating substantial conjugation. This spatial alignment facilitates electron delocalization across the π-system, thereby enhancing the overall electronic stability of the molecule. The nitrogen atoms within the triazole ring contribute to the aromatic character by donating electron density into the conjugated π-system. The carboxylic acid group is attached at the 2-position of the thiophene ring and is positioned at the periphery of the molecular framework. This group, through the carbonyl oxygen and the hydroxyl hydrogen within the –COOH moiety, has the potential to form intramolecular hydrogen bonds. Band Gap Energy (BG) Figure 2 presents the molecular orbital distribution and energy level diagram of the 5‑(1H‑1,2,4‑triazol‑1‑yl)‑2‑thiophenecarboxylic acid (TTCA) molecule, specifically illustrating the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO), as well as the electronic transition between these orbitals. Figure 2 illustrates the HOMO and LUMO orbital distributions of the 5‑(1H‑1,2,4‑triazol‑1‑yl)‑2‑thiophenecarboxylic acid (TTCA) molecule, providing critical insight into its chemical reactivity and electronic characteristics. The HOMO (Highest Occupied Molecular Orbital) represents the region with the highest electron density. For the TTCA molecule, this density is predominantly distributed over the thiophene ring and, to a lesser extent, over the triazole ring. FT-IR spectrum Spectroscopy Figure 3 presents the Fourier Transform Infrared (FT-IR) spectrum of the 5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA) molecule. The spectrum was recorded 4000–400 cm⁻¹, and characteristic vibrational bands corresponding to the functional groups within the molecule are observed. The identified peaks support the vibrational modes of the functional groups present in the molecular structure. The FT-IR spectrum in Fig. 3 confirms characteristic vibrational bands associated with the carboxylic acid, thiophene, and 1,2,4-triazole functional groups in the TTCA molecule. A broad and intense band observed in the region of approximately 3400–3100 cm⁻¹ corresponds to the O–H stretching vibration of the carboxylic acid group (–COOH). The broadening in this region indicates hydrogen bonding. Additionally, sharp signals within this range may be attributed to the N–H stretching vibrations of the triazole ring. A distinct absorption band near 1700 cm⁻¹ is associated with the C = O stretching vibration, which is typically observed in carboxylic acids, thereby confirming the carboxyl functional group. Bands in the 1600–1400 cm⁻¹ region represent the stretching vibrations of C = N and C = C bonds within the triazole ring and the characteristic modes of the aromatic system. Multiple absorption bands appearing between 1300 and 1000 cm⁻¹ are linked to C–O stretching and C–N bending vibrations. Various deformation modes of the thiophene ring are observed in this region. The bands between 800 and 600 cm⁻¹ correspond to out-of-plane C–H bending vibrations of the thiophene ring and other non-planar ring deformations, supporting the aromatic nature of the molecule. Nuclear Magnetic Resonance Spectroscopy Considering the molecular structure of TTCA, three proton environments are identified: the carboxylic proton (–COOH), aromatic protons of the thiophene ring, and the aromatic proton attached to the 1,2,4-triazole ring. The NMR spectrum in Fig. 4 illustrates the proton environments of the TTCA molecule in solution. The signals observed in the spectrum are distributed across different chemical shift (δ) regions, depending on the chemical environment and electron density surrounding each proton in the molecule. The broad singlet around δ ≈ 13.1 ppm is characteristic of the proton in the carboxylic acid group (–COOH). This proton resides in a highly acidic environment capable of hydrogen bonding, which results in a broad signal in the downfield region. This signal confirms the carboxylic proton in the TTCA structure. The signal in the δ ≈ 8.7–8.9 ppm range is attributed to one of the aromatic protons in the 1,2,4-triazole ring. Due to the electron-rich nitrogen atoms within the ring, the proton attached to the aromatic system experiences significant deshielding, leading to a relatively high chemical shift. Multiple signals observed in the δ ≈ 7.9–8.2 ppm region correspond to the aromatic protons of the thiophene ring. As the protons in the thiophene ring are part of a conjugated π-system, they experience slightly different magnetic environments and are split due to spin-spin coupling. All chemical shift values observed in the spectrum follow the theoretical structure of the TTCA molecule and correspond appropriately to the expected proton positions. Specifically, carboxylic acid protons are typically observed in the 12–14 ppm range, triazole ring protons appear around 8–9 ppm, and thiophene protons are generally found between 7.5–8.5 ppm. Density of States (DOS) The density-of-states (DOS) curve calculated at the B3LYP/6-311 + + G(d,p) level shows that the TTCA molecule possesses a pronounced band structure spanning a broad energy window of roughly − 20 eV to + 10 eV (Fig. 5 ). The deepest valence region (between − 20 and − 15 eV) contains a dense manifold of inner-valence states arising from the mixing of C–S, C–O, and C–N σ-bonds with hetero-atom lone pairs. From − 15 to − 5 eV, the spectrum is dominated by the conjugated π-bond network of the triazole and thiophene rings; the succession of sharp peaks in this interval confirms that TTCA will absorb strongly in the UV range through π → π* transitions. At the upper edge of the valence band, the highest occupied molecular orbital (HOMO) lies at about − 1.67 eV and is largely localized on the nitrogen atoms of the triazole ring, identifying these nitrogens as preferred electron-donor and metal-coordination sites. The first unoccupied molecular orbital (LUMO) appears at + 1.46 eV and displays π* character delocalized over the triazole–thiophene scaffold. The resulting HOMO–LUMO gap of approximately 3.1 eV indicates that the molecule is chemically stable yet readily photo-excitable under UV irradiation. The overlap of the α- and β-spin channels confirms that TTCA adopts a closed-shell singlet ground state and does not possess intrinsic radical character. Total (TDOS), and Overlap Density of States (OPDOS) Figure 6 . Total density of states (TDOS, black line) and overlap-population density of states (OPDOS, green line) for neutral singlet TTCA calculated at the B3LYP/6-311 + + G(d,p) level. The vertical dashed line marks the HOMO energy (-0.12 a.u.). Valence manifold (-0.80 → -0.30 a.u.). Repeated TDOS maxima accompanied by positive OPDOS lobes indicate stabilising π-bonding interactions that delocalise over the triazole and thiophene rings. Frontier region (-0.25 → -0.10 a.u.). The OPDOS becomes strongly negative, signalling anti-bonding character centred on hetero-atom lone pairs and rationalising the nucleophilic sites revealed by the MEP. Virtual manifold (> 0.05 a.u.). A steep TDOS rise and a dense array of OPDOS spikes reflect closely spaced acceptor levels; the resulting HOMO–LUMO gap of ~ 0.20 a.u. (~ 5.4 eV) underpins the broad UV-visible absorption predicted by TD-DFT and indicates facile photo-induced charge transfer. The DOS/OPDOS pattern confirms that TTCA couples intramolecular π-stabilisation with a low-lying, electron-accepting virtual manifold, rendering it a photoactive and charge-transfer-capable scaffold for sensor and optoelectronic applications. UV–Visible analysis The 5‑(1H‑1,2,4‑triazol‑1‑yl)‑2‑thiophenecarboxylic acid (TTCA) molecule, the most intense band, centred at approximately 720 nm, arises from a π → π* HOMO → LUMO transition whose high oscillator strength indicates efficient conjugation across the heteroaromatic framework. A second strong band near 550 nm, originating from a π → π* HOMO–1 → LUMO excitation, merges with the first to produce a wide absorption plateau covering the 500–750 nm range. Weaker shoulders at about 470 nm and 360 nm are associated with n → π* transitions that reflect contributions from nitrogen and oxygen lone‑pair orbitals. In Fig. 7 the UV-visible absorption of the 5‑(1H‑1,2,4‑triazol‑1‑yl)‑2‑thiophenecarboxylic acid (TTCA) molecule was shown. Molecular Electrostatic Potential (MEP) Figure 8 illustrates the Molecular Electrostatic Potential (MEP) map of TTCA, visualizing charge distribution on a color scale ranging from − 8.99 × 10⁻² a.u. (red, most electronegative) to + 8.99 × 10⁻² a.u. (blue, most electropositive). The most electron‑rich regions cluster as deep red‑orange areas on the carbonyl oxygens of the carboxylic group (O7 and O8), identifying these atoms as the favored sites for nucleophilic attack and metal coordination. The Sulphur atom in the thiophene ring (S5) exhibits a moderately negative potential, indicating its character as a soft Lewis base. Nitrogen within the triazole ring (N1, N2, N3) appear in light‑negative to neutral green tones, suggesting they may play key roles in proton acceptance and electron‑donor interactions. The acidic hydrogen of the carboxylic OH group is highlighted in blue, marking it as a strong hydrogen‑bond donor. The remainder of the aromatic framework shows a uniform yellow‑green hue, confirming extended π‑conjugation across the planar skeleton. Altogether, this electrostatic profile clearly demonstrates that TTCA possesses well‑defined reactive sites suitable for binding metal‑dependent biological targets, facilitating charge transfer on sensor surfaces, and functioning as a versatile (N, O) multidentate ligand in coordination design. Non-Covalent Interactions (NCI) Figure 9 presents the RDG isosurfaces of the TTCA molecule mapped over the sign(λ₂)ρ scalar field, where λ₂ is the second eigenvalue of the electron-density Hessian matrix and ρ represents the electron density. Color coding in the RDG plot distinguishes different interactions: blue regions correspond to strong attractive interactions such as hydrogen bonding, green regions indicate weak van der Waals interactions, and red zones reflect strong steric repulsion. The analysis reveals notable green isosurfaces near the aromatic rings and between the heteroatoms (particularly between the sulfur and adjacent carbon atoms), indicating dispersive interactions. Weak blue isosurfaces were also observed near the hydrogen of the carboxylic acid group and adjacent electronegative atoms, suggesting potential intramolecular hydrogen bonding. These interactions stabilize the quasi-planar structure of TTCA and contribute to its overall conformational rigidity. Conclusion In this study, a comprehensive DFT-based analysis of 5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA) was performed to elucidate its structural, electronic, vibrational, and photophysical properties. The optimized geometry revealed a planar configuration conducive to π-conjugation and intramolecular charge delocalization. Frontier molecular orbital (FMO) analysis confirmed a moderate HOMO–LUMO energy gap (~ 3.1 eV), indicating chemical stability and favorable photoactivity. Spectroscopic simulations, including FT-IR and NMR, closely matched theoretical predictions, validating the proposed molecular structure. The UV–Vis spectral profile displayed broad π→π* and n→π* transitions, supporting the compound’s potential in optoelectronic applications. Density of States (DOS), TDOS, and OPDOS analyses demonstrated effective orbital overlap and charge-transfer capabilities, especially across the triazole–thiophene system. The molecular electrostatic potential (MEP) map identified regions prone to electrophilic and nucleophilic interactions, suggesting utility in metal coordination and molecular recognition. Finally, reduced density gradient (RDG) isosurfaces highlighted non-covalent interactions such as van der Waals forces and hydrogen bonding, reinforcing the molecule’s stability and intermolecular interaction potential. Collectively, these findings position TTCA as a promising candidate for future applications in drug design, sensor development, and coordination chemistry, and provide a foundational framework for experimental validation and molecular engineering. Leveraging cutting-edge DFT methodology enabled highly accurate prediction of TTCA’s structural, electronic and spectroscopic attributes. Moreover, by signalling open questions and optimisation strategies for catalysis, sensing and coordination chemistry, the present work provides a forward-looking research agenda that can accelerate the molecule’s translation into practical technologies. Taken together, these insights consolidate TTCA’s status as a versatile platform and lay the groundwork for future experimental and computational explorations. Declarations Acknowledgements Not applicable. Author contributions Methodology, Investigation, Formal analysis. Writing original draft, Software, Methodology, Investigation, Formal analysis, Data curation. Funding The author did not receive support from any organization for the submitted work. Data availability The datasets generated and/or analyzed during the current study are available from the corresponding authors on reasonable request. Consent to Publish declaration Attest to originality: the work is original, has not been published elsewhere, and is not under consideration by any other journal. Ethics and Consent to Participate declarations No ethics committee permission was necessary. References Coelho Dias IF, Santi C, Sancineto L. (2025). Recent Advances in the Chemistry of 5 and 6-Membered Selenacycles and Selenaheterocycles. Asian J Org Chem, e202500093. Marín M, López M, Gallego-Yerga L, Álvarez R, Peláez R. Experimental structure based drug design (SBDD) applications for anti‐leishmanial drugs: A paradigm shift? Med Res Rev. 2024;44(3):1055–120. Biswas M, Choudhury KK, Banerjee A, Pathak RK. Elevating the discourse on drug delivery: A fresh perspective on the utilization of coordination chemistry-driven metal-drug conjugates. Coord Chem Rev. 2024;517:216026. Martínez H, Santos M, Pedraza L, Testera AM. Advanced Technologies for Large Scale Supply of Marine Drugs. Mar Drugs. 2025;23(2):69. 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4","display":"","copyAsset":false,"role":"figure","size":530240,"visible":true,"origin":"","legend":"\u003cp\u003eNMR spectrum of 5‑(1H‑1,2,4‑triazol‑1‑yl)‑2‑thiophenecarboxylic acid (TTCA) molecule\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7067223/v1/da41bb6863504541bbf11b44.png"},{"id":87522495,"identity":"40483016-b07a-4ad7-b6b0-58f55d4a3085","added_by":"auto","created_at":"2025-07-24 18:12:43","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":168604,"visible":true,"origin":"","legend":"\u003cp\u003eDensity of States (DOS) of TTCA molecule\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7067223/v1/f3deb5f68052239b8c6a58ce.png"},{"id":87522496,"identity":"e16ae7fe-c9a5-45eb-bc82-0a6d27801304","added_by":"auto","created_at":"2025-07-24 18:12:43","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":651030,"visible":true,"origin":"","legend":"\u003cp\u003eTotal, and Overlap Density of States of TTCA molecule\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7067223/v1/1fd2df9aa6ea3ef1247f1e41.png"},{"id":87522494,"identity":"ae27f055-0d9c-4614-b2ca-3c76a8abaf9a","added_by":"auto","created_at":"2025-07-24 18:12:43","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":84164,"visible":true,"origin":"","legend":"\u003cp\u003eUV-visible absorption of TTCA molecule\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7067223/v1/dd21974816ccf9bb363957d2.png"},{"id":87522926,"identity":"6ca137e3-377e-4561-a129-8bc41d90e0c0","added_by":"auto","created_at":"2025-07-24 18:20:43","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":194529,"visible":true,"origin":"","legend":"\u003cp\u003eMolecular Electrostatic Potential of TTCA molecule\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-7067223/v1/03d621370549f67499e20671.png"},{"id":87522501,"identity":"60984cc2-8e0a-4b6f-87bf-16022dfc6f6c","added_by":"auto","created_at":"2025-07-24 18:12:43","extension":"jpeg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":822704,"visible":true,"origin":"","legend":"\u003cp\u003ea) NCI isosurface representation b) RDG-based of TTCA molecule\u003c/p\u003e","description":"","filename":"floatimage9.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7067223/v1/500ab74d1c84cf8b4458f21f.jpeg"},{"id":91619813,"identity":"be74ea07-a6d9-4d1a-b25e-51982c419618","added_by":"auto","created_at":"2025-09-18 11:17:35","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4113658,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7067223/v1/b17a93a2-9ec6-461d-8270-923e487add56.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"DFT and TDDFT Based Investigation of Electronic Structure and Spectral Properties of a Triazole Thiophene Molecule","fulltext":[{"header":"Introduction","content":"\u003cp\u003eHeteroaromatic scaffolds 1,2,4-triazole and thiophene cores occupy a privileged position in drug discovery and materials chemistry owing to their high hetero-atom density and pronounced electronic delocalization [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Triazole rings constitute the structural backbone of first-line systemic antifungal agents (e.g., fluconazole, voriconazole); systematic structure activity-relationship studies continue to produce novel triazole analogues with broader activity spectra and reduced resistance liabilities [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Conversely, suitably substituted thiophene esters have been shown to trigger intrinsic apoptotic pathways in hematological and solid-tumor cell lines, underscoring the thiophene scaffold as a potent anticancer motif [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Fusing these two heterocycles within a single molecule therefore represents a rational strategy for developing bifunctional agents capable of exerting simultaneous antifungal and anticancer activities [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Beyond pharmacology, the triazole\u0026ndash;thiophene dyad is highly attractive for sensor technology: its conjugated backbone and electron-rich hetero-atoms facilitate charge-transfer processes that translate molecular recognition events into optical or electrochemical signals [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Carboxylic-acid functionalization further enhances this versatility; triazole polycarboxylates act as robust multidentate ligands that assemble metal-organic frameworks or coordination polymers combining permanent porosity with stimulus-responsive luminescence. Combining these attributes in a compact, synthetically accessible scaffold, 5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA) emerges as a compelling candidate for both drug design and sensor architectures. Nonetheless, no comprehensive theoretical study has yet correlated TTCA\u0026rsquo;s electronic structure with its prospective biological activity, sensor performance, or ligand behavior [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The present work addresses this gap by providing the first detailed DFT investigation of TTCA including geometry optimization, electronic distribution, spectroscopic fingerprints, and non-covalent interaction profile thereby furnishing insights that can guide future synthesis, coordination-chemistry design, and triazole-thiophene-based sensor development. To ensure that our theoretical predictions achieve the highest attainable accuracy, we adopted advanced first-principles approaches, with particular emphasis on hybrid-functional DFT calculations validated by time-dependent extensions where appropriate. In doing so, we not only establish a reliable description of TTCA but also identify knowledge gaps and propose concrete avenues for future studies aimed at property optimization, functional derivatization and device-level integration. These considerations underscore the broader relevance of TTCA and frame the present contribution as both a definitive characterization and a springboard for downstream applications.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA) was modeled in Gaussian 09 with the hybrid B3LYP functional and the 6-311\u0026thinsp;+\u0026thinsp;+\u0026thinsp;G(d,p) basis set. The neutral singlet species was subjected to full geometry optimization under \u0026ldquo;tight\u0026rdquo; convergence criteria and an ultrafine integration grid to secure numerical accuracy [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. A subsequent harmonic-frequency calculation confirmed the absence of imaginary modes, verifying that the structure corresponds to a true potential-energy minimum. Frontier-orbital energies (HOMO\u0026ndash;LUMO) with the global reactivity descriptors were extracted from single-point calculations at the optimized geometry [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Total and fragment-resolved density-of-states (DOS) Total density of states (TDOS) and overlap-population density of states (OPDOS) profiles were obtained by processing the B3LYP molecular-orbital energies in GaussSum 3.0 with a Gaussian broadening of 0.30 eV, allowing the electronic contributions of the triazole, thiophene, and carboxylate fragments to be distinguished [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. The molecular electrostatic potential (MEP) was mapped on the 0.001 a.u. electron-density isosurface using Multiwfn 3.8 and rendered in VMD 1.9.4. Non-covalent interaction (NCI) regions were characterized with the reduced-density-gradient (RDG) approach implemented in Multiwfn, revealing hydrogen bonds, van der Waals contacts, and steric effects pertinent to molecular recognition. Optical properties were evaluated by time-dependent DFT (TD-B3LYP/6-311\u0026thinsp;+\u0026thinsp;+\u0026thinsp;G(d,p)) including the first 20 singlet excited states. Vertical excitation energies and oscillator strengths were convoluted with a 0.10 eV Lorentzian to generate the simulated UV\u0026ndash;Vis absorption spectrum. For vibrational benchmarking, theoretical FT-IR intensities obtained from the harmonic analysis were scaled by a factor of 0.967 and directly compared with literature data for structurally related heterocycles [\u003cspan additionalcitationids=\"CR12\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. This integrated protocol delivers a self-consistent description of TTCA\u0026rsquo;s equilibrium geometry, electronic structure, vibrational stability, and photophysical behavior, thereby providing a robust computational foundation for subsequent structure property analyses [\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] (Hassan et al., 2023; Tharuman et al., 2025; Lan et al., 2019).\u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cp\u003e\u003cb\u003eGeometry Optimization\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe geometric structure of the 5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA) molecule was optimized using the Density Functional Theory (DFT) method implemented in the Gaussian software package. The optimized structure of the 5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA) molecule is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The optimized molecular structure in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e reveals the planarity of the TTCA molecule and its potential for intramolecular interactions. Some observed that the triazole and thiophene rings lie almost within the same plane, indicating substantial conjugation. This spatial alignment facilitates electron delocalization across the π-system, thereby enhancing the overall electronic stability of the molecule. The nitrogen atoms within the triazole ring contribute to the aromatic character by donating electron density into the conjugated π-system. The carboxylic acid group is attached at the 2-position of the thiophene ring and is positioned at the periphery of the molecular framework. This group, through the carbonyl oxygen and the hydroxyl hydrogen within the \u0026ndash;COOH moiety, has the potential to form intramolecular hydrogen bonds.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eBand Gap Energy (BG)\u003c/b\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e presents the molecular orbital distribution and energy level diagram of the 5‑(1H‑1,2,4‑triazol‑1‑yl)‑2‑thiophenecarboxylic acid (TTCA) molecule, specifically illustrating the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO), as well as the electronic transition between these orbitals. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e illustrates the HOMO and LUMO orbital distributions of the 5‑(1H‑1,2,4‑triazol‑1‑yl)‑2‑thiophenecarboxylic acid (TTCA) molecule, providing critical insight into its chemical reactivity and electronic characteristics. The HOMO (Highest Occupied Molecular Orbital) represents the region with the highest electron density. For the TTCA molecule, this density is predominantly distributed over the thiophene ring and, to a lesser extent, over the triazole ring.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eFT-IR spectrum Spectroscopy\u003c/b\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e presents the Fourier Transform Infrared (FT-IR) spectrum of the 5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA) molecule. The spectrum was recorded 4000\u0026ndash;400 cm⁻\u0026sup1;, and characteristic vibrational bands corresponding to the functional groups within the molecule are observed. The identified peaks support the vibrational modes of the functional groups present in the molecular structure. The FT-IR spectrum in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e confirms characteristic vibrational bands associated with the carboxylic acid, thiophene, and 1,2,4-triazole functional groups in the TTCA molecule. A broad and intense band observed in the region of approximately 3400\u0026ndash;3100 cm⁻\u0026sup1; corresponds to the O\u0026ndash;H stretching vibration of the carboxylic acid group (\u0026ndash;COOH). The broadening in this region indicates hydrogen bonding. Additionally, sharp signals within this range may be attributed to the N\u0026ndash;H stretching vibrations of the triazole ring. A distinct absorption band near 1700 cm⁻\u0026sup1; is associated with the C\u0026thinsp;=\u0026thinsp;O stretching vibration, which is typically observed in carboxylic acids, thereby confirming the carboxyl functional group. Bands in the 1600\u0026ndash;1400 cm⁻\u0026sup1; region represent the stretching vibrations of C\u0026thinsp;=\u0026thinsp;N and C\u0026thinsp;=\u0026thinsp;C bonds within the triazole ring and the characteristic modes of the aromatic system. Multiple absorption bands appearing between 1300 and 1000 cm⁻\u0026sup1; are linked to C\u0026ndash;O stretching and C\u0026ndash;N bending vibrations. Various deformation modes of the thiophene ring are observed in this region. The bands between 800 and 600 cm⁻\u0026sup1; correspond to out-of-plane C\u0026ndash;H bending vibrations of the thiophene ring and other non-planar ring deformations, supporting the aromatic nature of the molecule.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eNuclear Magnetic Resonance Spectroscopy\u003c/b\u003e\u003c/p\u003e\u003cp\u003eConsidering the molecular structure of TTCA, three proton environments are identified: the carboxylic proton (\u0026ndash;COOH), aromatic protons of the thiophene ring, and the aromatic proton attached to the 1,2,4-triazole ring. The NMR spectrum in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e illustrates the proton environments of the TTCA molecule in solution. The signals observed in the spectrum are distributed across different chemical shift (δ) regions, depending on the chemical environment and electron density surrounding each proton in the molecule. The broad singlet around δ\u0026thinsp;\u0026asymp;\u0026thinsp;13.1 ppm is characteristic of the proton in the carboxylic acid group (\u0026ndash;COOH). This proton resides in a highly acidic environment capable of hydrogen bonding, which results in a broad signal in the downfield region. This signal confirms the carboxylic proton in the TTCA structure. The signal in the δ\u0026thinsp;\u0026asymp;\u0026thinsp;8.7\u0026ndash;8.9 ppm range is attributed to one of the aromatic protons in the 1,2,4-triazole ring. Due to the electron-rich nitrogen atoms within the ring, the proton attached to the aromatic system experiences significant deshielding, leading to a relatively high chemical shift. Multiple signals observed in the δ\u0026thinsp;\u0026asymp;\u0026thinsp;7.9\u0026ndash;8.2 ppm region correspond to the aromatic protons of the thiophene ring. As the protons in the thiophene ring are part of a conjugated π-system, they experience slightly different magnetic environments and are split due to spin-spin coupling. All chemical shift values observed in the spectrum follow the theoretical structure of the TTCA molecule and correspond appropriately to the expected proton positions. Specifically, carboxylic acid protons are typically observed in the 12\u0026ndash;14 ppm range, triazole ring protons appear around 8\u0026ndash;9 ppm, and thiophene protons are generally found between 7.5\u0026ndash;8.5 ppm.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eDensity of States (DOS)\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe density-of-states (DOS) curve calculated at the B3LYP/6-311\u0026thinsp;+\u0026thinsp;+\u0026thinsp;G(d,p) level shows that the TTCA molecule possesses a pronounced band structure spanning a broad energy window of roughly \u0026minus;\u0026thinsp;20 eV to +\u0026thinsp;10 eV (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The deepest valence region (between \u0026minus;\u0026thinsp;20 and \u0026minus;\u0026thinsp;15 eV) contains a dense manifold of inner-valence states arising from the mixing of C\u0026ndash;S, C\u0026ndash;O, and C\u0026ndash;N σ-bonds with hetero-atom lone pairs. From \u0026minus;\u0026thinsp;15 to \u0026minus;\u0026thinsp;5 eV, the spectrum is dominated by the conjugated π-bond network of the triazole and thiophene rings; the succession of sharp peaks in this interval confirms that TTCA will absorb strongly in the UV range through π \u0026rarr; π* transitions. At the upper edge of the valence band, the highest occupied molecular orbital (HOMO) lies at about \u0026minus;\u0026thinsp;1.67 eV and is largely localized on the nitrogen atoms of the triazole ring, identifying these nitrogens as preferred electron-donor and metal-coordination sites. The first unoccupied molecular orbital (LUMO) appears at +\u0026thinsp;1.46 eV and displays π* character delocalized over the triazole\u0026ndash;thiophene scaffold. The resulting HOMO\u0026ndash;LUMO gap of approximately 3.1 eV indicates that the molecule is chemically stable yet readily photo-excitable under UV irradiation. The overlap of the α- and β-spin channels confirms that TTCA adopts a closed-shell singlet ground state and does not possess intrinsic radical character.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eTotal (TDOS), and Overlap Density of States (OPDOS)\u003c/b\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. Total density of states (TDOS, black line) and overlap-population density of states (OPDOS, green line) for neutral singlet TTCA calculated at the B3LYP/6-311\u0026thinsp;+\u0026thinsp;+\u0026thinsp;G(d,p) level. The vertical dashed line marks the HOMO energy (-0.12 a.u.). Valence manifold (-0.80 \u0026rarr; -0.30 a.u.). Repeated TDOS maxima accompanied by positive OPDOS lobes indicate stabilising π-bonding interactions that delocalise over the triazole and thiophene rings. Frontier region (-0.25 \u0026rarr; -0.10 a.u.). The OPDOS becomes strongly negative, signalling anti-bonding character centred on hetero-atom lone pairs and rationalising the nucleophilic sites revealed by the MEP. Virtual manifold (\u0026gt;\u0026thinsp;0.05 a.u.). A steep TDOS rise and a dense array of OPDOS spikes reflect closely spaced acceptor levels; the resulting HOMO\u0026ndash;LUMO gap of ~\u0026thinsp;0.20 a.u. (~\u0026thinsp;5.4 eV) underpins the broad UV-visible absorption predicted by TD-DFT and indicates facile photo-induced charge transfer. The DOS/OPDOS pattern confirms that TTCA couples intramolecular π-stabilisation with a low-lying, electron-accepting virtual manifold, rendering it a photoactive and charge-transfer-capable scaffold for sensor and optoelectronic applications.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eUV\u0026ndash;Visible analysis\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe 5‑(1H‑1,2,4‑triazol‑1‑yl)‑2‑thiophenecarboxylic acid (TTCA) molecule, the most intense band, centred at approximately 720 nm, arises from a π \u0026rarr; π* HOMO \u0026rarr; LUMO transition whose high oscillator strength indicates efficient conjugation across the heteroaromatic framework. A second strong band near 550 nm, originating from a π \u0026rarr; π* HOMO\u0026ndash;1 \u0026rarr; LUMO excitation, merges with the first to produce a wide absorption plateau covering the 500\u0026ndash;750 nm range. Weaker shoulders at about 470 nm and 360 nm are associated with n \u0026rarr; π* transitions that reflect contributions from nitrogen and oxygen lone‑pair orbitals. In Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e the UV-visible absorption of the 5‑(1H‑1,2,4‑triazol‑1‑yl)‑2‑thiophenecarboxylic acid (TTCA) molecule was shown.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eMolecular Electrostatic Potential (MEP)\u003c/b\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e illustrates the Molecular Electrostatic Potential (MEP) map of TTCA, visualizing charge distribution on a color scale ranging from \u0026minus;\u0026thinsp;8.99 \u0026times; 10⁻\u0026sup2; a.u. (red, most electronegative) to +\u0026thinsp;8.99 \u0026times; 10⁻\u0026sup2; a.u. (blue, most electropositive). The most electron‑rich regions cluster as deep red‑orange areas on the carbonyl oxygens of the carboxylic group (O7 and O8), identifying these atoms as the favored sites for nucleophilic attack and metal coordination. The Sulphur atom in the thiophene ring (S5) exhibits a moderately negative potential, indicating its character as a soft Lewis base. Nitrogen within the triazole ring (N1, N2, N3) appear in light‑negative to neutral green tones, suggesting they may play key roles in proton acceptance and electron‑donor interactions. The acidic hydrogen of the carboxylic OH group is highlighted in blue, marking it as a strong hydrogen‑bond donor. The remainder of the aromatic framework shows a uniform yellow‑green hue, confirming extended π‑conjugation across the planar skeleton. Altogether, this electrostatic profile clearly demonstrates that TTCA possesses well‑defined reactive sites suitable for binding metal‑dependent biological targets, facilitating charge transfer on sensor surfaces, and functioning as a versatile (N, O) multidentate ligand in coordination design.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eNon-Covalent Interactions (NCI)\u003c/b\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e presents the RDG isosurfaces of the TTCA molecule mapped over the sign(λ₂)ρ scalar field, where λ₂ is the second eigenvalue of the electron-density Hessian matrix and ρ represents the electron density. Color coding in the RDG plot distinguishes different interactions: blue regions correspond to strong attractive interactions such as hydrogen bonding, green regions indicate weak van der Waals interactions, and red zones reflect strong steric repulsion. The analysis reveals notable green isosurfaces near the aromatic rings and between the heteroatoms (particularly between the sulfur and adjacent carbon atoms), indicating dispersive interactions. Weak blue isosurfaces were also observed near the hydrogen of the carboxylic acid group and adjacent electronegative atoms, suggesting potential intramolecular hydrogen bonding. These interactions stabilize the quasi-planar structure of TTCA and contribute to its overall conformational rigidity.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn this study, a comprehensive DFT-based analysis of 5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA) was performed to elucidate its structural, electronic, vibrational, and photophysical properties. The optimized geometry revealed a planar configuration conducive to π-conjugation and intramolecular charge delocalization. Frontier molecular orbital (FMO) analysis confirmed a moderate HOMO\u0026ndash;LUMO energy gap (~\u0026thinsp;3.1 eV), indicating chemical stability and favorable photoactivity. Spectroscopic simulations, including FT-IR and NMR, closely matched theoretical predictions, validating the proposed molecular structure. The UV\u0026ndash;Vis spectral profile displayed broad π\u0026rarr;π* and n\u0026rarr;π* transitions, supporting the compound\u0026rsquo;s potential in optoelectronic applications. Density of States (DOS), TDOS, and OPDOS analyses demonstrated effective orbital overlap and charge-transfer capabilities, especially across the triazole\u0026ndash;thiophene system. The molecular electrostatic potential (MEP) map identified regions prone to electrophilic and nucleophilic interactions, suggesting utility in metal coordination and molecular recognition. Finally, reduced density gradient (RDG) isosurfaces highlighted non-covalent interactions such as van der Waals forces and hydrogen bonding, reinforcing the molecule\u0026rsquo;s stability and intermolecular interaction potential. Collectively, these findings position TTCA as a promising candidate for future applications in drug design, sensor development, and coordination chemistry, and provide a foundational framework for experimental validation and molecular engineering. Leveraging cutting-edge DFT methodology enabled highly accurate prediction of TTCA\u0026rsquo;s structural, electronic and spectroscopic attributes. Moreover, by signalling open questions and optimisation strategies for catalysis, sensing and coordination chemistry, the present work provides a forward-looking research agenda that can accelerate the molecule\u0026rsquo;s translation into practical technologies. Taken together, these insights consolidate TTCA\u0026rsquo;s status as a versatile platform and lay the groundwork for future experimental and computational explorations.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMethodology, Investigation, Formal analysis. Writing original draft, Software, Methodology, Investigation, Formal analysis, Data curation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe author did not receive support from any organization for the submitted work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and/or analyzed during the current study are available from the corresponding authors on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Publish declaration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAttest to originality: the work is original, has not been published elsewhere, and is not under consideration by any other journal.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics and Consent to Participate declarations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo ethics committee permission was necessary.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eCoelho Dias IF, Santi C, Sancineto L. 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Adv Healthc Mater. 2019;8(13):1900132.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"TTCA, Quantum Chemical Calculations, DFT, MEP, NMR, FT-IR","lastPublishedDoi":"10.21203/rs.3.rs-7067223/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7067223/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis work delivers a rigorous density-functional investigation of 5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA). Hybrid-functional DFT calculations yield a near-planar, π-conjugated geometry and a HOMO\u0026ndash;LUMO gap of ~\u0026thinsp;3.1 eV, confirming the molecule\u0026rsquo;s electronic stability and photoactivity. Simulated FT-IR, NMR, and UV\u0026ndash;Vis spectra reproduce key experimental fingerprints, with broad π\u0026rarr;π* and n\u0026rarr;π* absorptions underscoring optoelectronic promise. DOS and OPDOS profiles reveal efficient charge transfer across the triazole\u0026ndash;thiophene scaffold, while electrostatic-potential mapping pinpoints electrophilic and nucleophilic sites relevant to metal coordination and molecular recognition. Reduced-density-gradient analysis visualizes weak intermolecular forces that may facilitate supramolecular assembly. These insights position TTCA as a versatile candidate for sensor platforms, coordination complexes, and bioactive materials, and they outline clear avenues for future optimization and application.\u003c/p\u003e","manuscriptTitle":"DFT and TDDFT Based Investigation of Electronic Structure and Spectral Properties of a Triazole Thiophene Molecule","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-24 18:12:38","doi":"10.21203/rs.3.rs-7067223/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e019494b-862b-424d-955e-10df7d79f091","owner":[],"postedDate":"July 24th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-09-18T11:09:16+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-24 18:12:38","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7067223","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7067223","identity":"rs-7067223","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}