Light driven trans-to-cis isomerization of stilbene-like ligands in fac-[Re(CO)3(NN)(trans-L)]+ and luminescence of their photoproducts

The photochemistry and photophysics of the fac-[Re(CO)(3)(NN)(L)](+) complexes, NN = polypyridyl ligands and L = stilbene-like ligands, in acetonitrile solution and in poly(methyl methacrylate) (PMMA) polymer film have been reported. Under irradiation, the complexes exhibit trans-to-cis photoassisted isomerization of the coordinated stilbene-like ligand. The quantum yields are determined by absorption changes as well as by H-1 NMR spectra. The increasing luminescence as the photoproduct, fac-[Re(CO)(3)(NN)(cis-L)](+), is formed is assigned to the change of the lowest lying excited state from (IL)-I-3 to (MLCT)-M-3 Changes in absorption and emission spectra are also similar for the complexes in PMMA film, a suitable medium for device application based on their properties. The emission maxima of these complexes exhibit hypsochromic shifts as the medium rigidity increases, and the result is discussed based on the luminescence rigidochromic effect. Time-resolved infrared spectroscopy, TRIR, in combination with other techniques, characterized the excited state electronic properties of the fac-[Re(CO)(3)(phen)(bpe)]PF6 complex, where bpe is 1,2-bis(4-pyridyl)ethylene. The competitive intramolecular energy transfer is also investigated by analyzing photophysical and photochemical properties of binuclear complexes containing the (phen)Re-1(CO)(3) subunit bridged by trans-1,2-bis(4-pyridyl)ethylene. (c) 2005 Elsevier B.V. All rights reserved.