Collini Melissa A, Thomas Michael B, Bandi Venugopal, Karr Paul A, D'Souza Francis
Department of Chemistry, University of North Texas, 1155 Union Circle, #305070, Denton, TX 76203-5017, USA.
Department of Physical Sciences and Mathematics, Wayne State College, 111 Main Street, Wayne, Nebraska, 68787, USA.
Chemistry. 2017 Mar 28;23(18):4450-4461. doi: 10.1002/chem.201700200. Epub 2017 Mar 3.
The efficiency and mechanism of electron- and energy-transfer events occurring in both natural and synthetic donor-acceptor systems depend on their distance, relative orientation, and the nature of the surrounding media. Fundamental knowledge gained from model studies is key to building efficient energy harvesting and optoelectronic devices. Faster charge separation and slower charge recombination in donor-acceptor systems is often sought out. In our continued effort to build donor-acceptor systems using near-IR sensitizers, in the present study, we report ground and excited-state charge transfer in newly synthesized, directly linked tetrads featuring bisdonor (donor=phenothiazine and ferrocene), BF -chelated azadipyrromethane (azaBODIPY) and C entities. The tetrads synthesized using multi-step synthetic procedure revealed strong charge-transfer interactions in the ground state involving the donor and azaBODIPY entities. The near-IR emitting azaBODIPY acted as a photosensitizing electron acceptor along with fullerene whereas the phenothiazine and ferrocene entities acted as electron donors. The triads (bisdonor-azaBODIPY) and tetrads revealed ultrafast photoinduced charge separation leading to D -azaBODIPY -C and D -azaBODIPY-C (D=phenothiazine or ferrocene) charge separated states from the femtosecond transient absorption spectral studies in both polar and nonpolar solvent media. The charge-separated states populated the triplet excited state of azaBODIPY prior returning to the ground state.
在天然和合成供体-受体系统中发生的电子和能量转移事件的效率和机制取决于它们之间的距离、相对取向以及周围介质的性质。从模型研究中获得的基础知识是构建高效能量收集和光电器件的关键。人们通常寻求供体-受体系统中更快的电荷分离和更慢的电荷复合。在我们持续努力使用近红外敏化剂构建供体-受体系统的过程中，在本研究中，我们报道了新合成的、直接相连的四联体中的基态和激发态电荷转移，该四联体具有双供体（供体=吩噻嗪和二茂铁）、BF -螯合氮杂二吡咯甲烷（氮杂BODIPY）和C实体。使用多步合成程序合成的四联体在基态下显示出涉及供体和氮杂BODIPY实体的强电荷转移相互作用。发射近红外光的氮杂BODIPY与富勒烯一起作为光敏电子受体，而吩噻嗪和二茂铁实体作为电子供体。通过飞秒瞬态吸收光谱研究，在极性和非极性溶剂介质中，三联体（双供体-氮杂BODIPY）和四联体显示出超快的光诱导电荷分离，导致形成D -氮杂BODIPY -C和D -氮杂BODIPY-C（D=吩噻嗪或二茂铁）电荷分离态。电荷分离态在返回基态之前填充了氮杂BODIPY的三重激发态。
