Photoluminescence Electron-Transfer Quenching of Rhenium(I) Rectangles with Amines

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2006-09, Vol.110 (37), p.10683-10689
• Main Authors: Thanasekaran, P, Liao, Rong-Tang, Manimaran, Bala, Liu, Yen-Hsiang, Chou, Pi-Tai, Rajagopal, S, Lu, Kuang-Lieh
• Format: Article
• Language: English
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp060391p

Electron-transfer (ET) reactions from aromatic amines to excited states of rhenium(I)-based molecular rectangles [{Re(CO)3(μ-bpy)Br}{Re(CO)3(μ-L)Br}]2 (bpy = 4,4‘-bipyridine, L = 4,4‘-dipyridylacetylene (dpa), I; L = 4,4‘-dipyridylbutadiyne (dpb), II; and L = 1,4-bis(4‘-pyridylethynyl)benzene (bpeb), III) were investigated in a dichloromethane solution using luminescence quenching techniques. Direct evidence for the ET reaction was obtained from the detection of the amine cation radical in this system using time-resolved transient absorption spectroscopy. The values of the luminescence quenching rate constants, k q, of the 3MLCT excited state of Re(I) rectangles with amines were found to be higher than those for the monomeric Re(I) complexes and other Re(I)-based metallacyclophanes. The observed k q values were correlated well with the driving force (ΔG°) for the ET reactions. In addition, a semiclassical theory of ET was successfully applied to the photoluminescence quenching of Re(I) rectangles with amines.