Lingerfelt David B, Lestrange Patrick J, Radler Joseph J, Brown-Xu Samantha E, Kim Pyosang, Castellano Felix N, Chen Lin X, Li Xiaosong
Department of Chemistry, University of Washington , Seattle, Washington 98195, United States.
Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
J Phys Chem A. 2017 Mar 9;121(9):1932-1939. doi: 10.1021/acs.jpca.6b12099. Epub 2017 Feb 24.
Materials and molecular systems exhibiting long-lived electronic coherence can facilitate coherent transport, opening the door to efficient charge and energy transport beyond traditional methods. Recently, signatures of a possible coherent, recurrent electronic motion were identified in femtosecond pump-probe spectroscopy experiments on a binuclear platinum complex, where a persistent periodic beating in the transient absorption signal's anisotropy was observed. In this study, we investigate the excitonic dynamics that underlie the suspected electronic coherence for a series of binuclear platinum complexes exhibiting a range of interplatinum distances. Results suggest that the long-lived coherence can only result when competitive electronic couplings are in balance. At longer Pt-Pt distances, the electronic couplings between the two halves of the binuclear system weaken, and exciton localization and recombination is favored on short time scales. For short Pt-Pt distances, electronic couplings between the states in the coherent superposition are stronger than the coupling with other excitonic states, leading to long-lived coherence.
展现出长寿命电子相干性的材料和分子系统能够促进相干输运，为超越传统方法的高效电荷和能量输运打开大门。最近，在对一种双核铂配合物进行的飞秒泵浦 - 探测光谱实验中，发现了可能存在的相干、周期性电子运动的特征，在该实验中观察到瞬态吸收信号各向异性中存在持续的周期性拍频。在本研究中，我们针对一系列具有不同铂间距的双核铂配合物，研究了疑似电子相干性背后的激子动力学。结果表明，只有当竞争性电子耦合达到平衡时，才会产生长寿命相干性。在较长的铂 - 铂间距下，双核系统两半部分之间的电子耦合减弱，激子在短时间尺度上更倾向于局域化和复合。对于较短的铂 - 铂间距，相干叠加态中的态之间的电子耦合强于与其他激子态的耦合，从而导致长寿命相干性。
