Department of Chemistry, University of North Texas, 1155 Union Circle, # 305070, Denton, Texas 76203-5017, United States.
Department of Chemistry, Indian Institute of Technology, Indore 453552, India.
J Phys Chem B. 2021 Apr 29;125(16):4067-4075. doi: 10.1021/acs.jpcb.0c09996. Epub 2021 Apr 19.
The effect of acceptor strength on excited-state charge transfer (CT) and charge separation (CS) in central phenothiazine (PTZ)-derived symmetric (PTZ-(TCBD-TPA)) and asymmetric (PTZ-(TCBD/DCNQ-TPA)) push-pull conjugates, in which triphenylamine (TPA) acts as end capping and 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) and cyclohexa-2,5-diene-1,4-ylidene-expanded TCBD (DCNQ) act as electron acceptor units, is reported. Due to strong push-pull effects, intramolecular CT was observed in the ground state, extending the absorption into the near-infrared region. Electrochemical, spectroelectrochemical, and computational studies coupled with energy-level calculations predicted both and to be efficient candidates for ultrafast CT. Subsequent femtosecond transient absorption studies along with global target analysis, performed in both polar and nonpolar solvents, confirmed such processes in which the CS was efficient in asymmetric , having both TCBD and DCNQ acceptors in polar benzonitrile, while in toluene, only CT was witnessed. This work highlights the significance of the number and strength of electron acceptor entities and the role of solvent polarity in multimodular push-pull systems to achieve ultrafast CS.
受主强度对中心吩噻嗪（PTZ）衍生的对称（PTZ-（TCBD-TPA））和不对称（PTZ-（TCBD/DCNQ-TPA））推-拉共轭物中激发态电荷转移（CT）和电荷分离（CS）的影响的报告，其中三苯胺（TPA）作为端封端，1,1,4,4-四氰基丁二烯（TCBD）和环己-2,5-二烯-1,4-亚基扩展 TCBD（DCNQ）作为电子受体单元。由于强烈的推-拉效应，在基态观察到分子内 CT，将吸收扩展到近红外区域。电化学、光谱电化学和计算研究以及能级计算预测和都是超快 CT 的有效候选物。随后在极性和非极性溶剂中进行的飞秒瞬态吸收研究以及全局目标分析证实了这一过程，其中 CS 在具有 TCBD 和 DCNQ 受体的极性苯腈中的不对称性中是有效的，而在甲苯中只观察到 CT。这项工作强调了电子受体实体的数量和强度以及溶剂极性在实现超快 CS 的多模块推-拉系统中的重要性。
