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

Abstract

Four mixed-ligand complexes were prepared and formulated as [Ln(H₂OBA)(H₂PZDC)] and [Ln(H₂OBA)(H₂PDC)] {Ln = La & Gd; H₂OBA = 4,4-oxybisbenzoic acid; H₂PDC = 2,3-pyridinedicarboxylic acid; H₂PZDC = 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 °C for complexes 3, 5, and 7.

Keywords:

• Mixed-ligand
• bimetallic complexes
• lanthanide ion
• 4-nitrophenol

Acknowledgments

V.O. Adimula. is grateful to TWAS-CIIT for the 2017 TWAS-CIIT Fellowship awarded for part of this research at the COMSATS University, Islamabad, Abbottabad Campus, Pakistan.

Disclosure statement

No potential conflict of interest was reported by the authors.