Tailoring Transition Intensity of Ruthenium(II) Complexes with π-Elongated Phenyl Ligands: Experimental and Computational Insights

Tailoring Transition Intensity of Ruthenium(II) Complexes with π-Elongated Phenyl Ligands: Experimental and Computational Insights | 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 Tailoring Transition Intensity of Ruthenium(II) Complexes with π-Elongated Phenyl Ligands: Experimental and Computational Insights Zi Ying Yeoh, Yoshitada Morikawa, Mohammad B. Kassim, Siow-Ping Tan, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7964711/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 12 Jan, 2026 Read the published version in Structural Chemistry → Version 1 posted 8 You are reading this latest preprint version Abstract A series of novel ruthenium(II) complexes bearing π -elongated phenyl ligands have been synthesized via a 3-step reaction involving Ru(phen) 2 Cl 2 and functionalised phenanthroline ligands (phen- p -RCA; phen = phenanthroline, R = H, OCH 3 , or NO 2 ; CA = cinnamic acid/chloride) to evaluate the substituent effects on metal-to-ligand charge transfer (MLCT) absorption. The complexes were characterised by CNHS elemental analysis and IR, NMR, and UV-Vis spectroscopies. Complementary DFT/TDDFT calculations were employed to probe the electronic factors governing transition intensity. The molar extinction coefficient ( ε ) of the MLCT band increased in the order NO 2 < H < OCH 3 , with the methoxy OCH 3 group enhancing transition dipole moment through broader transition density distribution, while NO 2 group displayed the opposite trend. Computational investigation on π -elongation revealed that increasing ligand conjugation enhanced the existing MLCT bands and introduced new low-energy intra-ligand charge transfer (ILCT) transitions. Transition density and frontier molecular orbital analyses revealed reduced HOMO–LUMO gaps, increased ligand participation, and higher ε values, particularly in the ILCT region, largely independent of substituent type. Additionally, substituents show minimal effects on MLCT transitions, whereas NO 2 -substituted complexes exhibited stronger ILCT bands due to carbon–nitrogen orbital hybridization. Structural modifications also influenced photophysical behaviour: removal of amide functional groups decreased dihedral angles, improved planarity, and enhanced π -conjugation, leading to increased ε . Incorporation of nitrogen-containing moieties also boosted ε via lone-pair electron donation. Overall, these findings highlight the critical roles of π -elongation, substituent effects, and specific functional groups in tailoring the absorption features of Ru(II) complexes, providing valuable guidelines for optimizing photophysical performance. Ruthenium π-elongated computational molar extinction coefficient intra-ligand charge transfer Full Text Additional Declarations No competing interests reported. Supplementary Files ESIFiguresTablesStructuralChemistry.docx Cite Share Download PDF Status: Published Journal Publication published 12 Jan, 2026 Read the published version in Structural Chemistry → Version 1 posted Editorial decision: Revision requested 28 Nov, 2025 Reviews received at journal 17 Nov, 2025 Reviewers agreed at journal 07 Nov, 2025 Reviewers agreed at journal 05 Nov, 2025 Reviewers invited by journal 04 Nov, 2025 Editor assigned by journal 04 Nov, 2025 Submission checks completed at journal 03 Nov, 2025 First submitted to journal 27 Oct, 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. 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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-7964711","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":544595171,"identity":"7006a119-2c74-44a5-8549-99d72141f96f","order_by":0,"name":"Zi Ying Yeoh","email":"","orcid":"","institution":"Tunku Abdul Rahman University of Management and Technology","correspondingAuthor":false,"prefix":"","firstName":"Zi","middleName":"Ying","lastName":"Yeoh","suffix":""},{"id":544595173,"identity":"864effe4-06e0-4c31-a934-70861ee80e8e","order_by":1,"name":"Yoshitada Morikawa","email":"","orcid":"","institution":"The University of Osaka","correspondingAuthor":false,"prefix":"","firstName":"Yoshitada","middleName":"","lastName":"Morikawa","suffix":""},{"id":544595174,"identity":"c3451d35-251f-4679-b8de-5f9f2deddf35","order_by":2,"name":"Mohammad B. 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Insights","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"structural-chemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"stuc","sideBox":"Learn more about [Structural Chemistry](https://www.springer.com/journal/11224)","snPcode":"11224","submissionUrl":"https://submission.nature.com/new-submission/11224/3","title":"Structural Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer 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transfer (MLCT) absorption. The complexes were characterised by CNHS elemental analysis and IR, NMR, and UV-Vis spectroscopies. Complementary DFT/TDDFT calculations were employed to probe the electronic factors governing transition intensity. The molar extinction coefficient (\u003cem\u003eε\u003c/em\u003e) of the MLCT band increased in the order NO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;\u0026lt;\u0026thinsp;H\u0026thinsp;\u0026lt;\u0026thinsp;OCH\u003csub\u003e3\u003c/sub\u003e, with the methoxy OCH\u003csub\u003e3\u003c/sub\u003e group enhancing transition dipole moment through broader transition density distribution, while NO\u003csub\u003e2\u003c/sub\u003e group displayed the opposite trend. Computational investigation on \u003cem\u003eπ\u003c/em\u003e-elongation revealed that increasing ligand conjugation enhanced the existing MLCT bands and introduced new low-energy intra-ligand charge transfer (ILCT) transitions. Transition density and frontier molecular orbital analyses revealed reduced HOMO\u0026ndash;LUMO gaps, increased ligand participation, and higher \u003cem\u003eε\u003c/em\u003e values, particularly in the ILCT region, largely independent of substituent type. Additionally, substituents show minimal effects on MLCT transitions, whereas NO\u003csub\u003e2\u003c/sub\u003e-substituted complexes exhibited stronger ILCT bands due to carbon\u0026ndash;nitrogen orbital hybridization. Structural modifications also influenced photophysical behaviour: removal of amide functional groups decreased dihedral angles, improved planarity, and enhanced \u003cem\u003eπ\u003c/em\u003e-conjugation, leading to increased \u003cem\u003eε\u003c/em\u003e. Incorporation of nitrogen-containing moieties also boosted \u003cem\u003eε\u003c/em\u003e via lone-pair electron donation. Overall, these findings highlight the critical roles of \u003cem\u003eπ\u003c/em\u003e-elongation, substituent effects, and specific functional groups in tailoring the absorption features of Ru(II) complexes, providing valuable guidelines for optimizing photophysical performance.\u003c/p\u003e","manuscriptTitle":"Tailoring Transition Intensity of Ruthenium(II) Complexes with π-Elongated Phenyl Ligands: Experimental and Computational Insights","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-14 23:52:26","doi":"10.21203/rs.3.rs-7964711/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-11-29T03:33:15+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-17T16:05:49+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"292595258328902788283327830812236871231","date":"2025-11-07T14:40:43+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"257673613276970142701129123272239339828","date":"2025-11-05T19:44:15+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-11-05T03:36:23+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-11-04T13:18:44+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-11-03T16:42:42+00:00","index":"","fulltext":""},{"type":"submitted","content":"Structural Chemistry","date":"2025-10-28T02:21:07+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"structural-chemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"stuc","sideBox":"Learn more about [Structural Chemistry](https://www.springer.com/journal/11224)","snPcode":"11224","submissionUrl":"https://submission.nature.com/new-submission/11224/3","title":"Structural Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"77930481-46a8-436f-94c5-99f8968f32f2","owner":[],"postedDate":"November 14th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-01-19T17:04:46+00:00","versionOfRecord":{"articleIdentity":"rs-7964711","link":"https://doi.org/10.1007/s11224-025-02719-9","journal":{"identity":"structural-chemistry","isVorOnly":false,"title":"Structural Chemistry"},"publishedOn":"2026-01-12 16:30:28","publishedOnDateReadable":"January 12th, 2026"},"versionCreatedAt":"2025-11-14 23:52:26","video":"","vorDoi":"10.1007/s11224-025-02719-9","vorDoiUrl":"https://doi.org/10.1007/s11224-025-02719-9","workflowStages":[]},"version":"v1","identity":"rs-7964711","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7964711","identity":"rs-7964711","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}