Abstract
A series of luminescent rhenium(I) monoynyl complexes, [Re(NN)(CO) 3(CCR)] (NN=bpy, t Bu 2bpy; R=C 6H 5, C 6H 4Cl-4, C 6H 4OCH 3-4, C 6H 4C 8H 17-4, C 6H 4C 6H 5, C 8H 17, C 4H 3S, C 4H 2SC 4H 3S, C 5H 4N), together with their homo- and hetero-metallic binuclear complexes, {Re(NN)(CO) 3(CCC 5H 4N)[M]} (NN=bpy, t Bu 2bpy; [M]=[Re{(CF 3) 2-bpy}(CO) 3]ClO 4, [Re(NO 2-phen)(CO) 3]ClO 4, W(CO) 5) have been synthesized and their electrochemical and photoluminescence behaviors determined. The structural characterization and electronic structures of selected complexes have also been studied. The luminescence origin of the rhenium(I) alkynyl complexes has been assigned as derived states of a [dπ(Re)→π*(NN)] metal-to-ligand charge transfer (MLCT) origin mixed with a [π(CCR)→π*(NN)] ligand-to-ligand charge transfer (LLCT) character. The assignments are further supported by extended Hückel molecular orbital (EHMO) calculations, which show that the LUMO mainly consists of π*(NN) character while the HOMO is dominated by the antibonding character of the ReCCR moiety resulted from the overlap of the dπ(Re) and π(CCR) orbitals.
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