Novel homobinuclear lanthanide(III) complexes with isonicotinoyl hydrazone: synthesis and coordination chemistry

Two novel homobinuclear lanthanide(III) complexes with isonicotinoyl hydrazone ligand [Ho2(L)3(H2O)](NO3)2·(OH)·3.5H2O (I) and [Lu2(L)3](OH)3 (II) (where HL=N,N′-diisonicotinoyl-2-hydroxy-5-methylisophthalaldehyde dihydrazone) have been synthesized and characterized by infrared spectra, elemental analyses, thermal analyses and UV–Vis techniques. The crystal structures of both complexes have been determined by X-ray diffraction analysis. In complex I, the two intramolecular holmium(III) centers have different coordination environments with nine and ten coordination numbers, respectively; however, in complex II, both lutetium(III) centers have the same structure with nine coordination number. In both complexes, the lanthanide(III) ions are intramolecularly bridged by three phenolic oxygen atoms forming a dimeric complex with Ho⋯Ho distance of 3.5398(7) and Lu⋯Lu distance of 3.3960(9) Å, respectively. L acts as a pentadentate ligand with keto-form coordination in both complexes as indicated by the results of crystal structures and infrared spectral analysis.