Gupta Pankaj K, Ileperuma Chamari V, Misra Rajneesh, D'Souza Francis
Department of Chemistry, Indian Institute of Technology Indore Indore 453552 India
Department of Chemistry, University of North Texas at Denton 1155 Union Circle, #305070 Denton TX 76203-5017 USA
Chem Sci. 2025 May 29;16(26):12122-12128. doi: 10.1039/d5sc02950c. eCollection 2025 Jul 2.
Among the several exceptional properties of fullerene, C, its electron acceptor property is a highly studied topic. This work demonstrates the superior electron acceptor property of C, even in the presence of a stronger electron acceptor(s) in multi-modular donor-acceptor constructs. For this, novel bis-phenothiazine-C donor-acceptor conjugates incorporating strong electron acceptors, tetracyanobutadiene (TCBD) or dicyanoquinodimethane (DCNQ), have been newly synthesized. In this molecular design, the TCBD and DCNQ electron acceptors were placed between the two phenothiazine entities, while the C was in the peripheral position of one of the phenothiazine entities. After establishing their molecular structure, intramolecular charge transfer in these systems was probed through optical and electrochemical measurements, while time-dependent DFT studies initially probed the ground and excited-state charge transfer. These studies established the role of C as an acceptor compared to TCBD and DCNQ due to the sandwiching of the latter electron acceptors between two phenothiazine electron donors, which modulates their overall electron-acceptor abilities. Femtosecond pump-probe studies, covering broad spatial and temporal scales, provided experimental evidence that C serves as the terminal electron acceptor, wherein the electron transfer product of C was spectrally possible to identify. These unprecedented findings present new opportunities for designing multi-redox entities featuring push-pull systems, paving the way for the next generation of efficient energy harvesting, photocatalytic, and optoelectronic applications.
在富勒烯C的几种特殊性质中，其电子受体性质是一个受到广泛研究的课题。这项工作证明了即使在多模块供体-受体结构中存在更强的电子受体的情况下，C仍具有卓越的电子受体性质。为此，新合成了包含强电子受体四氰基丁二烯（TCBD）或二氰基喹喔啉二甲烷（DCNQ）的新型双吩噻嗪-C供体-受体共轭物。在这种分子设计中，TCBD和DCNQ电子受体位于两个吩噻嗪实体之间，而C位于其中一个吩噻嗪实体的外围位置。在确定了它们的分子结构后，通过光学和电化学测量对这些体系中的分子内电荷转移进行了探测，而含时密度泛函理论研究首先探测了基态和激发态的电荷转移。这些研究确定了与TCBD和DCNQ相比，C作为受体的作用，这是由于后一种电子受体夹在两个吩噻嗪电子供体之间，从而调节了它们的整体电子受体能力。飞秒泵浦-探测研究覆盖了广泛的空间和时间尺度，提供了实验证据表明C作为终端电子受体，其中C的电子转移产物在光谱上是可以识别的。这些前所未有的发现为设计具有推挽系统的多氧化还原实体提供了新的机会，为下一代高效能量收集、光催化和光电子应用铺平了道路。
