Electronic Coupling between Two Amine Redox Sites through the 5,5′-Positions of Metal-Chelating 2,2′-Bipyridines

Nie, H.-J., Chen, X., Yao, C.-J., Zhong, Y.-W., Hutchison, G. R. and Yao, J. “Electronic Coupling between Two Amine Redox Sites through the 5,5′-Positions of Metal-Chelating 2,2′-Bipyridines” Chem. Eur. J. 2012 18(45) pp. 14497–14509. Online. The supplemental info is available here: Nie SI.

Electron delocalization of new mixed-valent (MV) systems with the aid of lateral metal chelation is reported. 2,2′-Bipyridine (bpy) derivatives with one or two appended di-_p_-anisylamino groups on the 5,5′-positions and a coordinated [Ru(bpy)₂] (bpy=2,2′-bipyridine), [Re(CO)₃Cl], or [Ir(ppy)₂] (ppy=2-phenylpyridine) component were prepared. The single-crystal molecular structure of the bis-amine ligand without metal chelation is presented. The electronic properties of these complexes were studied and compared by electrochemical and spectroscopic techniques and DFT/TDDFT calculations. Compounds with two di-_p_-anisylamino groups were oxidized by a chemical or electrochemical method and monitored by near-infrared (NIR) absorption spectral changes. Marcus–Hush analysis of the resulting intervalence charge-transfer transitions indicated that electron coupling of these mixed-valent systems is enhanced by metal chelation and that the iridium complex has the largest coupling. TDDFT calculations were employed to interpret the NIR transitions of these MV systems.