Desta G. Woldegiorgis, Ephriem T. Mengesha, N. Babu G., Maria Susai Boobalan, Taye B. Demissie, E. Teju
{"title":"对-N,N-(二烷基氨基)苄基-亚硒丙二腈及相关体系的双重荧光发射:直接激发基态扭转分子内电荷转移(TICT)构象的证据","authors":"Desta G. Woldegiorgis, Ephriem T. Mengesha, N. Babu G., Maria Susai Boobalan, Taye B. Demissie, E. Teju","doi":"10.4314/bcse.v38i5.17","DOIUrl":null,"url":null,"abstract":"The mechanism of dual fluorescence emission of a fluorophore is controversial ever since its first observation in p-N,N-dimethylaminobenzonitrile (DMABN). Excited state twisted intramolecular charge transfer (TICT) and planarized intramolecular charge transfer (PICT) models have been the two prominent theories used to explain the dual fluorescence mechanism in several systems. These mechanisms are based on excited state adiabatic structural changes of the fluorophore. Nevertheless, pieces of evidences based on excitation spectral measurements at different emission windows suggest the possibility of additional and/or alternative mechanisms based on ground state structural changes of the fluorophore. In this paper, we have presented a systematic steady-state absorption and fluorescence spectroscopy of a donor-πacceptor system, p-N,N-(dialkylamino)benzylidenemalononitrile, and related compounds in solvents of different polarities. The excitation spectrum of p-N,N-(dialkylamino) benzylidenemalononitrile is found to be dependent on the emission window. Furthermore, the emission spectra of the molecule are dependent on the excitation wavelength which suggest that the molecule consists of two stable ground state conformational isomers. The spectroscopic pieces of evidence together with results from DFT calculations are in favor of the solvent-induced ground state structural change of the fluorophore. Hence, two ground state conformers of p-N,N-(dialkylamino)benzylidenemalononitrile are attributed to the dual emission of the molecule. \nKEY WORDS: Dual fluorescence, Charge transfer, TICT, PICT, Excitation, Benzylidenemalononitriles \nBull. Chem. Soc. Ethiop. 2024, 38(5), 1413-1427. \nDOI: https://dx.doi.org/10.4314/bcse.v38i5.17 ","PeriodicalId":9501,"journal":{"name":"Bulletin of the Chemical Society of Ethiopia","volume":null,"pages":null},"PeriodicalIF":1.3000,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Dual fluorescence emission of p-N,N-(dialkylamino) benzyl-idenemalononitrile and related systems: Evidence for direct excitation of ground state twisted intramolecular charge transfer (TICT) conformer\",\"authors\":\"Desta G. Woldegiorgis, Ephriem T. Mengesha, N. Babu G., Maria Susai Boobalan, Taye B. Demissie, E. Teju\",\"doi\":\"10.4314/bcse.v38i5.17\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"The mechanism of dual fluorescence emission of a fluorophore is controversial ever since its first observation in p-N,N-dimethylaminobenzonitrile (DMABN). Excited state twisted intramolecular charge transfer (TICT) and planarized intramolecular charge transfer (PICT) models have been the two prominent theories used to explain the dual fluorescence mechanism in several systems. These mechanisms are based on excited state adiabatic structural changes of the fluorophore. Nevertheless, pieces of evidences based on excitation spectral measurements at different emission windows suggest the possibility of additional and/or alternative mechanisms based on ground state structural changes of the fluorophore. In this paper, we have presented a systematic steady-state absorption and fluorescence spectroscopy of a donor-πacceptor system, p-N,N-(dialkylamino)benzylidenemalononitrile, and related compounds in solvents of different polarities. The excitation spectrum of p-N,N-(dialkylamino) benzylidenemalononitrile is found to be dependent on the emission window. Furthermore, the emission spectra of the molecule are dependent on the excitation wavelength which suggest that the molecule consists of two stable ground state conformational isomers. The spectroscopic pieces of evidence together with results from DFT calculations are in favor of the solvent-induced ground state structural change of the fluorophore. Hence, two ground state conformers of p-N,N-(dialkylamino)benzylidenemalononitrile are attributed to the dual emission of the molecule. \\nKEY WORDS: Dual fluorescence, Charge transfer, TICT, PICT, Excitation, Benzylidenemalononitriles \\nBull. Chem. Soc. 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Dual fluorescence emission of p-N,N-(dialkylamino) benzyl-idenemalononitrile and related systems: Evidence for direct excitation of ground state twisted intramolecular charge transfer (TICT) conformer
The mechanism of dual fluorescence emission of a fluorophore is controversial ever since its first observation in p-N,N-dimethylaminobenzonitrile (DMABN). Excited state twisted intramolecular charge transfer (TICT) and planarized intramolecular charge transfer (PICT) models have been the two prominent theories used to explain the dual fluorescence mechanism in several systems. These mechanisms are based on excited state adiabatic structural changes of the fluorophore. Nevertheless, pieces of evidences based on excitation spectral measurements at different emission windows suggest the possibility of additional and/or alternative mechanisms based on ground state structural changes of the fluorophore. In this paper, we have presented a systematic steady-state absorption and fluorescence spectroscopy of a donor-πacceptor system, p-N,N-(dialkylamino)benzylidenemalononitrile, and related compounds in solvents of different polarities. The excitation spectrum of p-N,N-(dialkylamino) benzylidenemalononitrile is found to be dependent on the emission window. Furthermore, the emission spectra of the molecule are dependent on the excitation wavelength which suggest that the molecule consists of two stable ground state conformational isomers. The spectroscopic pieces of evidence together with results from DFT calculations are in favor of the solvent-induced ground state structural change of the fluorophore. Hence, two ground state conformers of p-N,N-(dialkylamino)benzylidenemalononitrile are attributed to the dual emission of the molecule.
KEY WORDS: Dual fluorescence, Charge transfer, TICT, PICT, Excitation, Benzylidenemalononitriles
Bull. Chem. Soc. Ethiop. 2024, 38(5), 1413-1427.
DOI: https://dx.doi.org/10.4314/bcse.v38i5.17
期刊介绍:
The Bulletin of the Chemical Society of Ethiopia (BCSE) is a triannual publication of the Chemical Society of Ethiopia. The BCSE is an open access and peer reviewed journal. The BCSE invites contributions in any field of basic and applied chemistry.