SYNTHESIS, CHARACTERIZATION AND VARIABLE-TEMPERATURE NUCLEAR-MAGNETIC-RESONANCE OF BIS(BIPYRIDINE)RUTHENIUM COMPLEXES CONTAINING DIHYDRAZONE LIGANDS

A series of dihydrazone and substituted dihydrazone derivatives of bia cetyl and of hydrazone and phenylhydrazone derivatives of 2-acetylpyri dine bind to [Ru(bipy)2Cl2] to give [Ru(bipy)2(L-L)][PF6]2 complexes { bipy = 2,2'-bipyridine; L-L = biacetyl di(phenylhydrazone) 1a, biacety l di[methyl(phenyl)hydrazone] 1b, biacetyl di(o-tolylhydrazone) 1c, bi acetyl di(dimethylhydrazone) 1d, biacetyl dihydrazone 1e, biacetyl di( benzaldehyde azine) lf, 2-acetylpyridine phenylhydrazone 1g, or 2-acet ylpyridine hydrazone 1h}. The structures of all complexes have been de termined using IR, UV/VIS, NMR and microanalysis. The proton NMR spect ra of 1a-1c show an unusual dependence on probe temperature with broad ened aromatic resonances, sharpening at both high and low temperature in the case of 1b and 1c. No emission was observed for complexes with two hydrazone moieties, whereas it was observed for 1g and 1h with one hydrazone. The molecular structure of 1a has been determined and show s a hydrazone phenyl group lying over each of the bipyridyl rings: spa ce group C2/c, a = 25.895(3), b = 10.505(1), c = 17.431(2) angstrom, b eta = 106.03(2)degrees and Z = 4.