Multimetallic ruthenium(II) complexes based on biimidazole and bibenzimidazole: effect of dianionic bridging ligands on redox and spectral properties
| Autor: | L. Morgan, A.K. Edwards, R.J. Shaver, Ram Sahai, D.P. Rillema, P. Matthews |
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| Rok vydání: | 1990 |
| Předmět: | |
| Zdroj: | Inorganic Chemistry. 29:167-175 |
| ISSN: | 1520-510X 0020-1669 |
| DOI: | 10.1021/ic00327a006 |
| Popis: | The preparation and properties of ruthenium(II) complexes containing the ligands 2,2{prime}-biimidazole (BiImH{sub 2}), 2,2{prime}-bibenzimidazole (BiBzImH{sub 2}), and 2,2{prime}-bipyridine (bpy) are reported. The complexes described are ((Ru(bpy){sub 2}){sub 2}BiIm){sup 2+} and the series (Ru-(bpy){sub n}(BiImH{sub 2}){sub 3{minus}n}){sup 2+}, (Ru(bpy){sub n}(BiBzImH{sub 2}){sub 3{minus}n}){sup 2+}, and (Ru(bpy){sub n}(BiBzImRu(bpy){sub 2}){sub 3{minus}n}){sup 2+}, n = 0-2. The redox potential for the first Ru{sup 3+/2+} couple shifted negatively from 1.26 to {minus}0.26 V vs SSCE as bpy ligands were replaced by BiImH{sub 2}, BiBzImH{sub 2}, and BiBzImRu(bpy){sub 2} ligands. Reductions were found in the {minus}1.5- to {minus}1.6-V range for complexes containing bypyridine ligands, but none were observed out to {minus}2.0 V for (Ru(BiImH{sub 2}){sub 3}){sup 2+} or (Ru(BiBzImH{sub 2}){sub 3}){sup 2+}. The complexes absorbed energy in the visible and UV regions of the spectrum and emitted radiation, with the exception of the tetrametallic species, in the 600-800-nm region. Estimates of the excited-state redox potentials revealed that the excited-state species were powerful reductants, but were weak oxidants. The (Ru{sup III}-(BiBzImRu{sup II}(bpy){sub 2}){sub 3}){sup 3+} cation absorbed in the near-infrared region at 12.2 {times} 10{sup 3} cm{sup {minus}1} in acetonitrile, but the absorption disappeared upon reduction to (Ru{sup II}(BiBzImRu{sup II}(bpy){sub 2}){sub 3}){sup 2+}. The position of the absorptionmore » manifold maximum varied linearly with the static and optical dielectric constant of the solvent. 45 refs., 12 figs., 3 tabs.« less |
| Databáze: | OpenAIRE |
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