Baitalik, Sujoy ; Florke, Ulrich ; Nag, Kamalaksha (2002) Homo- and heterobimetallic complexes of ruthenium(II) and osmium(II) with pyrazole-3,5-dicarboxylic acid and 2,2'-bipyridine as co-ligands. Synthesis, structure, stereochemistry, spectroscopy and redox activities Inorganica Chimica Acta, 337 . pp. 439-449. ISSN 0020-1693
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Official URL: http://linkinghub.elsevier.com/retrieve/pii/S00201...
Related URL: http://dx.doi.org/10.1016/S0020-1693(02)01113-1
Abstract
Mononuclear, homodinuclear and heterodinuclear ruthenium(II) and osmium(II) complexes of composition [(bpy)2Ru(H2pzdc)](ClO4)·3H2O (1), [(bpy)2Os(H2pzdc)](ClO4)·3H2O (2), [(bpy)2Ru(pzdc)Ru(bpy)2](ClO4)·H2O (3), [(bpy)2Os(pzdc)Os(bpy)2](ClO4)·H2O (4) and [(bpy)2Ru(pzdc)Os(bpy)2](ClO4)·H2O (5) have been synthesized with pyrazole-3,5-dicarboxylic acid (H3pzdc) and 2,2'-bipyridine (bpy). Complexes 3-5 isolated solely in the homochiral forms have been characterized by their 1H and {1H---1H} COSY NMR spectra. The crystal structures determined for 3 and 5 have revealed that the two compounds are isostructural and the diruthenium compound 3 is present in the rac(ΛΛ/ΔΔ) form, while the osmium---ruthenium compound 5 is present as the enantiomeric pair (ΛΛ and ΔΔ). The metal-centered oxidation and bipyridine-centred reduction in 1-5 take place reversibly. As compared with the diruthenium complex 3, the stepwise oxidation of the metal centers in the diosmium complex 4 take place at less positive potentials by 0.45 V. The equilibrium constants for the comproportionation reaction MIIMII+MIIIMIII⇔2MIIMIII are found to be almost equal (ca. 6×102) for the diruthenium and diosmium species. From pH-dependent redox potential measurements the acid dissociation constants for the mononuclear complexes 1 and 2 have been determined. The luminescence spectral behavior of the complexes have been investigated in methanol-ethanol (1:4) solution (at 300 K) and in glassy state (77 K) and the quantum yields for the ruthenium(II) complexes are reported.
Item Type: | Article |
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Source: | Copyright of this article belongs to Elsevier Science. |
Keywords: | Ruthenium(II) Complexes; Osmium(II) Complexes; Homo- and Heterodinuclear Complexes; Ru---OS Complexes; Crystal Structures; Electrochemistry; Chirality; Pyrazole-3,5-dicarboxylate Complexes |
ID Code: | 22743 |
Deposited On: | 24 Nov 2010 07:56 |
Last Modified: | 23 Jan 2011 15:35 |
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