Cheng Tao, Xiao Xuan, Zhang Lei, Liu Chun Y, Wang Li-Li, Meng Miao, Zhao Fang, Wang Hui, Ji Liang-Nian
Department of Chemistry, Jinan University, 601 Huang-Pu Avenue West, Guangzhou 510632, China.
Department of Chemistry, Tongji University, 1239 Siping Road, Shanghai 200092, China.
Phys Chem Chem Phys. 2017 Jan 18;19(3):1740-1745. doi: 10.1039/c6cp07582g.
Photoinduced electron transfer (ET) in Mo dimers, Mo(DAniF) (DAniF = N,N'-di(p-anisyl)formamidinate, E = O or S), has been studied by femtosecond transient spectral techniques. Using a 355 nm laser pulse, the δ electrons on the Mo-Mo quadruple bonds are selectively excited and subsequent charge separation yields diradicals [Mo]˙-ph-[Mo]˙ and [Mo]-ph˙-[Mo]˙. The charge separation (CS) and recombination (CR) rates are derived by fitting the decay kinetic data of the excited states. Surprisingly, it is found that the CR rate constants (k, ∼10 s) for [Mo]˙-ph-[Mo]˙ are larger than the data (k) for [Mo]-ph˙-[Mo]˙ by about one order of magnitude, although in the first case, the ET distance is doubled and the electronic coupling between the donor and acceptor is weaker. Optical analyses reveal that the free energy changes (ΔG°) for the two CR processes correspond to the δ → δ* and the metal (δ) to bridging ligand (π*) transition energies, respectively, and thus, the ET kinetics is dominated likely by the driving force (-ΔG°).
通过飞秒瞬态光谱技术研究了钼二聚体Mo(DAniF)（DAniF = N,N'-二（对茴香基）甲脒，E = O或S）中的光诱导电子转移（ET）。使用355 nm激光脉冲，Mo-Mo四重键上的δ电子被选择性激发，随后的电荷分离产生双自由基[Mo]˙-ph-[Mo]˙和[Mo]-ph˙-[Mo]˙。通过拟合激发态的衰减动力学数据得出电荷分离（CS）和复合（CR）速率。令人惊讶的是，发现[Mo]˙-ph-[Mo]˙的CR速率常数（k，~10 s）比[Mo]-ph˙-[Mo]˙的数据（k）大约大一个数量级，尽管在第一种情况下，ET距离加倍且供体和受体之间的电子耦合较弱。光学分析表明，两个CR过程的自由能变化（ΔG°）分别对应于δ→δ以及金属（δ）到桥连配体（π）的跃迁能量，因此，ET动力学可能由驱动力（-ΔG°）主导。
