Diastereoisomerically pure pyrazole-3,5-dicarboxylate-bridged dinuclear ruthenium(II) and osmium(II) complexes of 2,2′-bipyridine: structural, electrochemical and spectral studies

Pyrazole-3,5-dicarboxylate-bridged dinuclear ruthenium(II) and osmium(II) complexes of 2,2′-bipyridine of composition [(bpy)2Ru(pzdc)Ru(bpy)2](ClO4) · H2O (1) and [(bpy)2Os(pzdc)Os(bpy)2](ClO4) · H2O (2) have been obtained in high yield and have been separated to their homochiral (ΛΛ/ΔΔ) rac (1a, 2a) and heterochiral (ΛΔ/ΔΛ) meso (1b, 2b) diastereoisomers. The distinctive structural features of these diastereoisomers have been characterized by 1-D and 2-D 1H NMR spectroscopy. The X-ray crystal structure of rac-[(bpy)2Os(pzdc)Os(bpy)2](ClO4) · H2O (2a) has been determined. The electrochemical and electronic spectral studies have established that there remain difference in properties and hence difference in intermetallic communication between the diastereoisomeric forms in each case.