Ghosh Saptarshi, Roy Nayan, Singh T Sanjoy, Chattopadhyay Nitin
Department of Chemistry, Jadavpur University, Jadavpur, Kolkata 700032, India.
Department of Chemistry, Assam University, Silchar, Assam 788011, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2018 Jan 5;188:252-257. doi: 10.1016/j.saa.2017.07.006. Epub 2017 Jul 13.
The present work reports detailed photophysics of a coumarin based Schiff base, namely, (E)-7-(((8-hydroxyquinolin-2-yl)methylene)amino)-4-methyl-2H-chromen-2-one (HMC) in different solvents of varying polarity exploiting steady state absorption, fluorescence and time resolved fluorescence spectroscopy. The dominant photophysical features of HMC are discussed in terms of emission from an intramolecular charge transfer (ICT) excited state. Molecular orbital (MO) diagrams as obtained from DFT based computational analysis confirms the occurrence of charge transfer from 8'-hydroxy quinoline moiety of the molecule to the coumarin part. The notable difference in the photophysical response of HMC from its analogous coumarin (C480) lies in a lower magnitude of fluorescence quantum yield of the former, particularly in the solvents of low polarity, which is rationalized by considering the higher rate of non-radiative decay of HMC in apolar solvents. Phosphorescence emission as well as phosphorescence lifetime of HMC has also been reported in 77K frozen matrix.
本研究工作报道了一种基于香豆素的席夫碱，即(E)-7-(((8-羟基喹啉-2-基)亚甲基)氨基)-4-甲基-2H-色烯-2-酮(HMC)在不同极性溶剂中的详细光物理性质，采用稳态吸收、荧光和时间分辨荧光光谱法进行研究。从分子内电荷转移(ICT)激发态的发射角度讨论了HMC的主要光物理特性。基于密度泛函理论(DFT)的计算分析得到的分子轨道(MO)图证实了分子中8'-羟基喹啉部分向香豆素部分发生了电荷转移。HMC与其类似香豆素(C480)在光物理响应上的显著差异在于前者的荧光量子产率较低，尤其是在低极性溶剂中，这可以通过考虑HMC在非极性溶剂中较高的非辐射衰减速率来解释。还报道了HMC在77K冷冻基质中的磷光发射以及磷光寿命。
