Kojima Takahiko, Sakamoto Taisuke, Matsuda Yoshihisa
Department of Chemistry, Faculty of Sciences, Kyushu University, Hakozaki, Higashi-Ku, Fukuoka 812-8581, Japan.
Inorg Chem. 2004 Apr 5;43(7):2243-5. doi: 10.1021/ic035137f.
A Ru(II) complex having tris(2-pyridylmethl)amine (TPA) and 2,2'-bipyridine (bpy), [Ru(TPA)(bpy)]X(2) (X = ClO(4), PF(6)), exhibited a severe distortion of the coordination of the axial pyridine moiety of TPA due to steric hindrance. The complex showed interesting dissociation-binding behavior of the axial pyridine arm to form a solvent adduct with TPA ligation in a unique meridional tridentate fashion. The complex undergoes thermal dissociation to form solvent-coordinated species via an S(N)2-like mechanism with activation energy of 117 kJ/mol. In contrast, the complex showed reversible photochemical dissociation and rebinding via an S(N)1-like mechanism by MLCT irradiation. The photochemical dissociation was accelerated approximately 200-fold faster than the thermal process. The dissociation process involves selective binding behavior toward external ligands (solvents) with pi-acceptor character, which is indispensable, and no sigma-donating molecules could bind to the Ru(II) center. The guest molecule can be released upon photoirradiation after its thermal binding.
一种含有三（2 - 吡啶甲基）胺（TPA）和2,2'-联吡啶（bpy）的钌（II）配合物，[Ru(TPA)(bpy)]X₂（X = ClO₄、PF₆），由于空间位阻，TPA轴向吡啶部分的配位出现严重扭曲。该配合物表现出轴向吡啶臂有趣的解离 - 结合行为，以独特的经式三齿方式与TPA配位形成溶剂加合物。该配合物通过类似SN2的机制发生热解离，形成溶剂配位的物种，活化能为117 kJ/mol。相比之下，该配合物通过MLCT照射以类似SN1的机制表现出可逆的光化学解离和重新结合。光化学解离比热过程快约200倍。解离过程涉及对具有π受体特征的外部配体（溶剂）的选择性结合行为，这是必不可少的，并且没有σ供体分子能与Ru（II）中心结合。客体分子在热结合后经光照射可被释放。
