Syntheses and Characterization of a Pair of Isomers of Heteroleptic Bis(Bidentate) Ruthenium(II) Complexes with Two Different Monodentate Ligands |
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Authors: | Dr Mari Toyama Takako Takizawa Itaru Morita Prof Noriharu Nagao Dr Yusuke Kuramochi Prof Hitoshi Ishida |
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Institution: | 1. Current address: Osaka Prefecture University College of Technology, 26-12 Saiwaicho, Neyagawa, Osaka, 572-8572 Japan;2. Department of Applied Chemistry, School of Science and Technology, Meiji University, 1-1-1 Higashi-Mita, Tama-ku, Kawasaki, Kanagawa, 214-8571 Japan;3. Department of Chemistry, Graduate School of Science, Kitasato University, 1-15-1 Kitasato, Sagamihara, Kanagawa, 252-0373 Japan
Current address: Department of Chemistry, Faculty of Science Division II, Tokyo University of Science, 1–3 Kagurazaka, Shinjuku-ku, Tokyo, 162-8601 Japan;4. Department of Chemistry, Graduate School of Science, Kitasato University, 1-15-1 Kitasato, Sagamihara, Kanagawa, 252-0373 Japan |
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Abstract: | Two isomers of heteroleptic bis(bidentate) ruthenium(II) complexes with dimethyl sulfoxide (dmso) and chloride ligands, trans(Cl,Nbpy)- and trans(Cl,NHdpa)-Ru(bpy)Cl(dmso-S)(Hdpa)]+ (bpy: 2,2′-bipyridine; Hdpa: di-2-pyridylamine), are synthesized. This is the first report on the selective synthesis of a pair of isomers of cis-Ru(L)(L′)XY]n+ (L≠L′: bidentate ligands; X≠Y: monodentate ligands). The structures of the ruthenium(II) complexes are clarified by means of X-ray crystallography, and the signals in the 1H NMR spectra are assigned based on 1H–1H COSY spectra. The colors of the two isomers are clearly different in both the solid state and solution: the trans(Cl,Nbpy) isomer has a deep red color, whereas the trans(Cl,NHdpa) isomer is yellow. Although both complexes have intense absorption bands at λ≈440–450 nm, only the trans(Cl,Nbpy) isomer has a shoulder band at λ≈550 nm. DFT calculations indicate that the LUMOs of both isomers are the π* orbitals in the bpy ligand, and that the LUMO level of the trans(Cl,Nbpy) isomer is lower than that of the trans(Cl,NHdpa) isomer due to the trans effect of the Cl ligand; thus resulting in the appearance of the shoulder band. The HOMO levels are almost the same in both isomers. The energy levels are experimentally supported by cyclic voltammograms, in which these isomers have different reduction potentials and similar oxidation potentials. |
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Keywords: | density functional calculations isomers ligand effects ruthenium structure elucidation |
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