Probing Metal-to-Ligand Charge-Transfer Excited-State Mediated Ru (II)/Ru(III) Electronic Coupling in the Creutz-Taube Analogues

• Main Authors: Tian, Yi-Han, 田逸涵
• Other Authors: Chen, Yuan-Jang
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/05988567280736486646

碩士 === 輔仁大學 === 化學系 === 100 === In this work, we focused on the physical relationships between metal-to-ligand charge-transfer (MLCT) and intervalence charge-transfer (IVCT) optical transitions of the pyrazine-bridged Creutz-Taube (C-T) analogues which clearly indicate the role of the MLCT excited-state in mediating the terminal Ru(II)/Ru(III) electronic coupling. The two types of low energy IVCT absorption shapes of C-T series found in the mixture-solvent (CH3CN/D2O), trans-[{Ru(NH3)4L1}2(μ-pz)](PF6)4, L1 = NH3, py (pyridine), and etpy (4-ethyl-pyridine); [{mer-Ru(NH3)3L2}2-(μ-pz)](PF6)4, L2 = bpy (2,2′-bipyridine) and bpyam (2,2′-bipyridylamine); and [{Ru(NH3)4}2(2,5-dpp)](PF6)4, (2,5-dpp = 2,5-bis(2-pyridyl)pyrazine). It is easy to perceive the contrast between the observedly narrow IVCT band-width (v1/2 = 1410 cm-1~1790 cm-1) for L1 = NH3, py, etpy, and L2 = bpyam, and [{Ru(NH3)4}2(2,5-dpp)]4+ ions, and twice amplitude of observed IVCT band-width (v1/2 = 3780 cm-1) for L2 = bpy ion, also, the small E1/2 = 205 mV between ruthenium moieties of L2 = bpy ion is comparing with the E1/2 ranging 350 ~ 430mV of L1 = NH3, py, etpy, and L2 = bpyam, and [{Ru(NH3)4}2(2,5-dpp)]4+ ions, which implied the relatively weak coupling phenomenon of L2 = bpy ion. These observations demonstrate the significantly configurational mixing between terminally coordinated ligand and the bridged MLCT excited-states contribution to the terminal Ru(II)/Ru(III) electronic coupling.