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

IF 16.4 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Accounts of Chemical Research Pub Date : 2024-07-12 DOI:10.4314/bcse.v38i5.17

Desta G. Woldegiorgis, Ephriem T. Mengesha, N. Babu G., Maria Susai Boobalan, Taye B. Demissie, E. Teju

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引用次数: 0

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. 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

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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

自从在对-N,N-二甲基氨基苯腈（DMABN）中首次观察到荧光团的双重荧光发射机制以来，该机制一直存在争议。激发态扭曲分子内电荷转移（TICT）模型和平面化分子内电荷转移（PICT）模型一直是用于解释多个体系中双重荧光机制的两种著名理论。这些机制都是以荧光团激发态绝热结构变化为基础的。然而，基于不同发射窗口的激发光谱测量的一些证据表明，基于荧光团基态结构变化的其他和/或替代机制也是可能的。本文介绍了供体-π受体系统 p-N,N-（二烷基氨基）亚苄基丙二腈及相关化合物在不同极性溶剂中的系统稳态吸收和荧光光谱。研究发现，对-N,N-（二烷基氨基）亚苄基丙二腈的激发光谱与发射窗口有关。此外，该分子的发射光谱与激发波长有关，这表明该分子由两种稳定的基态构象异构体组成。光谱学证据和 DFT 计算结果都支持溶剂诱导的荧光团基态结构变化。因此，对-N,N-（二烷基氨基）亚苄基丙二腈的两种基态构象可归因于该分子的双发射。关键词：双荧光电荷转移 TICT PICT 激发苄叉丙二腈 Bull.Chem.Soc.2024, 38(5), 1413-1427. DOI: https://dx.doi.org/10.4314/bcse.v38i5.17

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来源期刊

Accounts of Chemical Research 化学-化学综合

CiteScore

31.40

自引率

1.10%

发文量

312

审稿时长

2 months

期刊介绍： Accounts of Chemical Research presents short, concise and critical articles offering easy-to-read overviews of basic research and applications in all areas of chemistry and biochemistry. These short reviews focus on research from the author’s own laboratory and are designed to teach the reader about a research project. In addition, Accounts of Chemical Research publishes commentaries that give an informed opinion on a current research problem. Special Issues online are devoted to a single topic of unusual activity and significance. Accounts of Chemical Research replaces the traditional article abstract with an article "Conspectus." These entries synopsize the research affording the reader a closer look at the content and significance of an article. Through this provision of a more detailed description of the article contents, the Conspectus enhances the article's discoverability by search engines and the exposure for the research.