Synthesis, characterization and catalytic studies of bimetallic heteronuclear complexes for the reduction of nitroaromatic compounds

Four mixed-ligand complexes were prepared and formulated as [Ln(H(2)OBA)(H(2)PZDC)] and [Ln(H(2)OBA)(H2PDC)] {Ln = La & Gd; H(2)OBA = 4,4-oxybisbenzoic acid; H2PDC = 2,3-pyridinedicarboxylic acid; H(2)PZDC = 2,3-pyrazinedicarboxylic acid}. The complexes were modified by a nickel/cobalt impregnation method to generate bimetallic complexes 1-8. Fourier transform infrared (FTIR) spectroscopy analysis of the bimetallic complexes indicated that the carboxylate coordinated to the lanthanide ion via the OH- group while the Ni2+ and Co2+ ions were preferentially bonded to the nitrogen donor ligand via the N- group. Complete catalytic reduction of 4-nitrophenol to 4-aminophenol by the Ni@ complexes gave a maximum reduction time of 37 minutes for complex 1 while complex 7 gave a reduction time of 21 minutes. The rate constants were observed to increase with an increase in temperature up to 50 degrees C for complexes 3, 5, and 7.