Synthesis, structure, and catalytic bromination of supramolecular oxovanadium complexes containing oxalate

Abstract

Three supramolecular complexes, [VO(phen)(C2O4)(H2O)]·CH3OH (1) [(VO)2(u2-C2O4)(C2O4)2(H2O)2]·L·H2O (2), and [(4,4′-bipyH2)0.5]+[VO2(2,6-dipic)]−·2H2O (3) (phen = 1,10-phenanthroline 4,4′-bipy = 4,4′-bipyridine, 2,6-dipic = 2,6-pyridinedicarboxylic, L = 1,4-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)benzene), have been prepared and characterized by elemental analysis, IR, and UV–vis spectroscopy and single-crystal diffraction analysis. Structural analysis shows that the three complexes all contain carboxylate and V=O moiety; vanadium of 1 and 2 are six coordinate with distorted octahedral geometry with N2O4 and O6 donor sets, respectively, while 3 is five coordinate with distorted trigonal bipyramidal geometry with a NO4 donor set. The complexes exhibit catalytic bromination activity in the single-pot reaction for the conversion of phenol red to bromophenol blue in H2O–DMF at 30 ± 0.5 C with pH 5.8, indicating that they can be considered as functional model vanadium-dependent haloperoxidases. In addition, electrochemical behaviors are also studied.