Nath Surjatapa, Bhattacharya Barnali, Sarkar Utpal, Singh T Sanjoy
Department of Chemistry, Assam University, Silchar, Assam, India.
Department of Physics, Assam University, Silchar, India.
J Fluoresc. 2022 Jul;32(4):1321-1336. doi: 10.1007/s10895-022-02905-6. Epub 2022 Apr 2.
In this work, a donor-acceptor substituted aromatic system ((E)-N-((E)-3-(4 (dimethylamino)phenyl) allylidene)-4-(trifluoromethyl) benzenamine (DPATB) has been synthesized and its detailed photophysics of intramolecular charge transfer process have been explored on the basis of steady state absorption, fluorescence and time resolved spectroscopy in combination with density functional theory calculations. Large solvent dependency fluorescence spectral shift and the calculated large excited state dipole moment clearly indicate an efficient charge transfer occurring from the donor group to the acceptor moiety in the excited state. Effect on addition of acid and pH on steady state spectral properties further reveals excited state charge transfer character. Quantum chemical calculations were performed in order to study the conformation and polarity of DPATB at their ground as well as excited electronic states. The HOMO and LUMO molecular orbital pictures are obtained at DFT level using B3LYP functional and 6-311 + g(d,p) basis set which clearly support excited state intramolecular charge transfer process. The molecular electrostatic potential maps for the optimized ground state, donor twisted and acceptor twisted geometry shed insight on the electrostatic potential and charge distribution in a system which gives information about the reacting site of the probe and nature of the reaction. In this work, detailed photophysics of excited state intramolecular charge transfer process in donor-acceptor system (DPATB) was evaluated using steady state and time-resolved fluorescence spectroscopy in combination with density functional theory calculations. Large solvent dependency fluorescence spectral shift and the calculated large excited state dipole moment clearly indicate an efficient charge transfer occurring in DPATB. Molecular orbital pictures as obtained from DFT based computational analysis reveals a significant change in the distribution of electron density upon transition from HOMO to LUMO which confirms an ICT process occurring from the donor group to the acceptor moiety in the excited state.
在本工作中，合成了一种供体-受体取代的芳香体系（(E)-N-((E)-3-(4-(二甲基氨基)苯基)亚烯丙基)-4-(三氟甲基)苯甲胺（DPATB）），并基于稳态吸收、荧光和时间分辨光谱结合密度泛函理论计算，对其分子内电荷转移过程的详细光物理性质进行了研究。较大的溶剂依赖性荧光光谱位移以及计算得到的较大激发态偶极矩清楚地表明，在激发态下从供体基团到受体部分发生了有效的电荷转移。酸的添加和pH对稳态光谱性质的影响进一步揭示了激发态电荷转移特性。进行了量子化学计算，以研究DPATB在基态以及激发电子态下的构象和极性。使用B3LYP泛函和6-311+g(d,p)基组在DFT水平上获得了HOMO和LUMO分子轨道图，这清楚地支持了激发态分子内电荷转移过程。优化后的基态、供体扭曲和受体扭曲几何结构的分子静电势图揭示了系统中的静电势和电荷分布，给出了有关探针反应位点和反应性质的信息。在本工作中，结合密度泛函理论计算，使用稳态和时间分辨荧光光谱对供体-受体体系（DPATB）中激发态分子内电荷转移过程的详细光物理性质进行了评估。较大的溶剂依赖性荧光光谱位移以及计算得到的较大激发态偶极矩清楚地表明DPATB中发生了有效的电荷转移。基于DFT的计算分析得到的分子轨道图显示，从HOMO到LUMO跃迁时电子密度分布发生了显著变化，这证实了在激发态下从供体基团到受体部分发生了ICT过程。
