title: Photoluminescence electron-transfer quenching of rhenium(I) rectangles with amines.
abstract: Electron-transfer (ET) reactions from aromatic amines to excited states of rhenium(I)-based molecular rectangles [{Re(CO)3(mu-bpy)Br}{Re(CO)3(mu-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, kq, 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 kq values were correlated well with the driving force (Delta G degrees) for the ET reactions. In addition, a semiclassical theory of ET was successfully applied to the photoluminescence quenching of Re(I) rectangles with amines.
authors.affiliation: Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan.
authors.forename: P
authors.initials: P
authors.lastname: Thanasekaran
authors.forename: Rong-Tang
authors.initials: RT
authors.lastname: Liao
authors.forename: Bala
authors.initials: B
authors.lastname: Manimaran
authors.forename: Yen-Hsiang
authors.initials: YH
authors.lastname: Liu
authors.forename: Pi-Tai
authors.initials: PT
authors.lastname: Chou
authors.forename: S
authors.initials: S
authors.lastname: Rajagopal
authors.forename: Kuang-Lieh
authors.initials: KL
authors.lastname: Lu