Kayanuma Megumi, Shoji Mitsuo, Shigeta Yasuteru
Center for Computational Sciences , University of Tsukuba , 1-1-1 Tennodai , Tsukuba , Ibaraki 305-8577 , Japan.
J Phys Chem A. 2019 Apr 4;123(13):2497-2502. doi: 10.1021/acs.jpca.8b11399. Epub 2019 Mar 13.
The photoinduced ligand exchange reaction of Ru(II) complexes in aqueous solution was studied using density functional theory (DFT). The optimized structures of the lowest triplet state of cis-[Ru(bpy)(CHCN)] (bpy = bipyridine), cis-[Ru(bpy)(NH)], and their monoaqua complexes were analyzed. The metal-centered (MC) structure was lower than the metal-to-ligand charge transfer (MLCT) structure for cis-[Ru(bpy)(CHCN)], whereas the MLCT structure was lower than the MC structure for cis-[Ru(bpy)(NH)]. Such a difference would correlate with the higher quantum yield of the former complex. For the monoaqua complexes, the most stable local minimum structure was the MC structure, in which the Ru-O and Ru-N ( trans to the oxygen) bonds were elongated. Therefore, the dissociation of the HO ligand would be preferred to that of the CHCN (or NH) ligand from the monoaqua intermediate, which might result in the reformation of the monoaqua intermediate, and thus, the formation of the bis-aqua product would take a longer time than that of the monoaqua intermediate.
采用密度泛函理论（DFT）研究了钌（II）配合物在水溶液中的光致配体交换反应。分析了顺式-[Ru(bpy)(CHCN)]（bpy = 联吡啶）、顺式-[Ru(bpy)(NH)]及其一水合配合物最低三重态的优化结构。对于顺式-[Ru(bpy)(CHCN)]，以金属为中心（MC）的结构低于金属到配体的电荷转移（MLCT）结构，而对于顺式-[Ru(bpy)(NH)]，MLCT结构低于MC结构。这种差异可能与前一种配合物较高的量子产率相关。对于一水合配合物，最稳定的局部极小值结构是MC结构，其中Ru - O键和Ru - N（与氧相对）键被拉长。因此，与从一水合中间体解离CHCN（或NH）配体相比，HO配体的解离更受青睐，这可能导致一水合中间体的重新形成，因此，二水合产物的形成比一水合中间体的形成需要更长时间。
