期刊
JOURNAL OF PHYSICAL CHEMISTRY B
卷 125, 期 16, 页码 4108-4119出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpcb.1c00120
关键词
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资金
- Portuguese Science Foundation [02/SAICT/2017, PTDC/QUI-QFI/31625/2017]
- Compete Centro 2020, Project Suprasol - Fundo Europeu de Desenvolvimento Regional (FEDER), through Programa Operacional Regional LISBOA (LISBOA2020) [LISBOA-01-0145-FEDER028365 - PTDC/QUI-QOR/28365/2017, LISBOA2020]
- project SunStorage -Harvesting and storage of solar energy - FEDER, through Programa Operacional Factores de Competitividade (COMPETE) 2020 -Operational Programme for Competitiveness and Internationalization (OPCI) [POCI-01-0145-FEDER016387]
- Fundacao para a Ciencia e a Tecnologia (FCT), the Portuguese Agency for Scientific Research
- FEDER through COMPETE
- FCT [UIDB/00313/2020, UIDP/00313/2020, UID/QUI/00100/2019, SFRH/BD/74351/2010]
- project SunStorage - Harvesting and storage of solar energy
- Project Hylight [031625]
- Fundação para a Ciência e a Tecnologia [SFRH/BD/74351/2010] Funding Source: FCT
This study investigates the characteristics of ESPT in indigo, the properties of different substitutions in solvents, and the pathways of excited-state deactivation. The photophysical properties and molecular structural features of indigo derivatives are discussed in relation to trans-cis photoisomerization and ESPT.
In indigo, excited state proton transfer (ESPT) is known to be associated with the molecular mechanism responsible for highly efficient radiationless deactivation. When this route is blocked (partially or totally), new deactivation routes become available. Using new green chemistry procedures, with favorable green chemistry metrics, monosubstitution and disubstitution of N group(s) in indigo, by tert-butoxy carbonyl groups, N-(tert-butoxycarbonyl)indigo (NtBOCInd) and N,N'-(tert-butoxycarbonyl)indigo (N,N'tBOCInd), respectively, were synthetically accomplished. The compounds display red to purple colors depending on the solvent and substitution. Different excited-state deactivation pathways were observed and found to be structure- and solvent-dependent. Trans-cis photoisomerization was found to be absent with NtBOCInd and present with N,N'tBOCInd in nonpolar solvents. Time-resolved fluorescence experiments revealed single-exponential decays for the two compounds which, linked to time-dependent density functional theory (TDDFT) studies, show that with NtBOCInd ESPT is extremely fast and barrierless-predicted to be 1 kJ mol(-1) in methylcyclohexane and 5 kJ mol(-1) in dimethylsulfoxide., which contrasts with similar to 11 kJ mol(-1) experimentally obtained for indigo. An alternative ESPT, competitive with the N-H center dot center dot center dot O=C intramolecular pathway, involving dimer units is also probed by TDDFT and found to be consistent with the experimentally observed time-resolved data. N,N'tBOCInd, where ESPT is precluded, shows solvent-dependent trans-cis/cis-trans photoisomerization and is surprisingly found to be more stable in the nonemissive cis conformation, whose deactivation to S-0 is found to be solvent-dependent.
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