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The Coumarin-Dimer Spring—The Struggle between Charge Transfer and Steric Interactions

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cris.lastimport.scopus2024-02-12T19:52:18Z
dc.abstract.enThe synthesis of a weakly coupled, strongly polarized coumarin dimer has been achieved for the first time. The three-step strategy comprises the Skattebøl formylation followed by the Knoevenagel reaction and the formation of a tertiary amide by using a peptide-type procedure. The molecule consists of two different coumarin moieties: One is a classical donor–acceptor system and the second one possesses a weaker amide donor at the 7-position. The polarized coumarin dimer can form an electronically conjugated structure possessing an electric dipole larger than that of 7-(dimethylamino)coumarin-3-carboxylic acid. The limited flexibility of the inter-coumarin connection results in stable conformers of different electric dipole moments and complex photophysics. In the solid state, this compound has a strongly bent conformation with the two coumarin units forming an angle of around 74°. In solution, two conformers are in equilibrium. The existence of the molecule as two conformers in the ground state has been confirmed by optical studies, and further corroborated by molecular calculations. The fluorescence spectra possess a unique feature: A charge-transfer band (ca. 550 nm) is visible only in nonpolar or weakly polar solvents. Optical spectroscopy studies coupled with molecular calculations allowed us to rationalize this phenomenon: The large amplitude of intramolecular motions is responsible for the conformational isomerization as well as producing a conical intersection between the potential energy surfaces of the excited singlet state and the ground state, which opens an internal conversion channel that effectively competes with the fluorescence of the conformers.
dc.affiliationUniwersytet Warszawski
dc.contributor.authorMorawski, Olaf
dc.contributor.authorSobolewski, Andrzej
dc.contributor.authorGryko, Daniel
dc.contributor.authorKielesiński, Łukasz
dc.contributor.authorDobrzycki, Łukasz
dc.date.accessioned2024-01-26T10:09:45Z
dc.date.available2024-01-26T10:09:45Z
dc.date.issued2017
dc.description.financeNie dotyczy
dc.description.number38
dc.description.volume23
dc.identifier.doi10.1002/CHEM.201701387
dc.identifier.issn0947-6539
dc.identifier.urihttps://repozytorium.uw.edu.pl//handle/item/122051
dc.identifier.weblinkhttps://doi.org/10.1002/chem.201701387
dc.languageeng
dc.pbn.affiliationchemical sciences
dc.relation.ispartofChemistry - A European Journal
dc.relation.pages9174-9184
dc.rightsClosedAccess
dc.sciencecloudnosend
dc.subject.enab initio calculations
dc.subject.enarenes
dc.subject.enconformation analysis
dc.subject.endonor–acceptor systems
dc.subject.endyes/pigments
dc.subject.enfluorescence
dc.titleThe Coumarin-Dimer Spring—The Struggle between Charge Transfer and Steric Interactions
dc.typeJournalArticle
dspace.entity.typePublication