title: Metal chelation-assisted amine-amine electronic coupling through the 4,4'-positions of 2,2'-bipyridine.
abstract: A redox-active diamine ligand, 4,4'-bis(di-p-anisylamino)-2,2'-bipyridine (NNbpy), has been prepared. Electrochemical and spectroscopic studies suggest that little electronic coupling is present between two amine groups in NNbpy. After chelation with Ru(bpy)2 (bpy is 2,2'-bipyridine), the resulting complex displays two N(•+/0) processes at +1.02 and +1.16 V versus Ag/AgCl. In the mixed-valent state, rich near-infrared absorptions have been observed, which are believed to consist of multiple metal-to-ligand charge transfer and intervalence charge transfer transitions in the low-energy region. These results suggest that the amine-amine electronic coupling has been enhanced by chelation with Ru(bpy)2. In contrast, no efficient electronic coupling can be realized by chelation with Ir(ppy)2 (ppy is 2'-phenylpyridine) or Re(CO)3Cl. A ruthenium ion-mediated electron transfer mechanism, instead of through-space coupling, has been proposed to explain this phenomenon. For the purpose of comparison, a monoamine-substituted bpy ligand and corresponding Ru(bpy)2 complex have been synthesized and studied. In addition, EPR, DFT, and TDDFT studies have been performed to complement the experimental results.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Photochemistry, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences , 2 Bei Yi Jie, Zhong Guan Cun, Beijing 100190, People's Republic of China.
authors.forename: Hai-Jing
authors.initials: HJ
authors.lastname: Nie
authors.forename: Wen-Wen
authors.initials: WW
authors.lastname: Yang
authors.forename: Ren-Hui
authors.initials: RH
authors.lastname: Zheng
authors.forename: Qiang
authors.initials: Q
authors.lastname: Shi
authors.forename: Hui
authors.initials: H
authors.lastname: Chen
authors.forename: Jiannian
authors.initials: J
authors.lastname: Yao
authors.forename: Yu-Wu
authors.initials: YW
authors.lastname: Zhong