Mitra Prajoy Kumar, Verma Preetika, Lakshmanna Yapamanu Adithya
School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram Vithura Thiruvananthapuram 695551 India
RSC Adv. 2025 Apr 17;15(16):12191-12201. doi: 10.1039/d5ra01814e. eCollection 2025 Apr 16.
Imine-based molecular systems have served as promising semi-conductive materials for applications in light-emitting diodes and photovoltaics. Benzylideneaniline, an imine-based molecular system, acts as a bioisostere of diarylethylenes such as stilbene and resveratrol, and plays a crucial role in pharmaceutical and biological applications. However, the excited-state dynamics of benzylideneanilines is less explored. In this context, we investigated 4'-(dimethylamino)benzylidene-4-nitroaniline (DMABNA), an imine-based donor-acceptor system, to unravel the excited-state dynamics. Here, we explored excited-state charge transfer dynamics and associated structural dynamics in various solvent environments through femtosecond transient absorption (fs-TA) and femtosecond fluorescence spectroscopic methods. The fs-TA measurements revealed distinct spectral and temporal features from cyclohexane to acetonitrile indicating that DMABNA essentially undergoes significant configurational changes in the excited state, leading to intramolecular charge transfer (ICT), particularly in polar environments. The fs-fluorescence measurements reveal the ultrashort lifetime (a few ps) of fluorescence across all the solvents indicating an effective non-radiative relaxation in the excited electronic state. These studies are corroborated by the computational analysis through DFT and TDDFT methods, wherein we predicted that DMABNA undergoes significant structural changes in the excited state (S) due to varying solvent polarity and viscosity. Such excited state molecular activity can play a significant role in the context of photo-initiated applications.
基于亚胺的分子体系已成为用于发光二极管和光伏应用的有前景的半导体材料。苄叉苯胺作为一种基于亚胺的分子体系，是诸如芪和白藜芦醇等二芳基乙烯的生物电子等排体，并且在药物和生物应用中发挥着关键作用。然而，苄叉苯胺的激发态动力学研究较少。在此背景下，我们研究了4'-(二甲氨基)苄叉-4-硝基苯胺（DMABNA），一种基于亚胺的供体-受体体系，以揭示其激发态动力学。在这里，我们通过飞秒瞬态吸收（fs-TA）和飞秒荧光光谱方法，探索了在各种溶剂环境中的激发态电荷转移动力学以及相关的结构动力学。fs-TA测量揭示了从环己烷到乙腈的不同光谱和时间特征，表明DMABNA在激发态基本上经历了显著的构型变化，导致分子内电荷转移（ICT），特别是在极性环境中。fs-荧光测量揭示了在所有溶剂中荧光的超短寿命（几皮秒），表明在激发电子态中存在有效的非辐射弛豫。这些研究通过密度泛函理论（DFT）和含时密度泛函理论（TDDFT）方法的计算分析得到了证实，其中我们预测由于溶剂极性和粘度的变化，DMABNA在激发态（S）会发生显著的结构变化。这种激发态分子活性在光引发应用的背景下可以发挥重要作用。
