A series of oxo-vanadium(IV) complexes containing mixed ligands of poly(pyrazolyl)borate and organic carboxylic acid: Synthesis, structural characterization and primary study of bromination reaction activities

A series of oxo-vanadium(IV) complexes: Tp∗VO(pzH∗)(CH3COO) (1), Tp∗VO(pzH∗)(CCl3COO) (2), Tp∗VO(pzH∗)(C6H5COO) (3), Tp∗VO(pzH∗)(m-NO2–C6H4COO)·CH3CN (4) and [Tp∗VO(pzH∗)(H2O)]+[m-NO2–C6H4–SO3]−·CH3OH (5) (Tp∗ = hydrotris(3,5-dimethylpyrazolyl)borate; pzH∗ = 3,5-dimethylpyrazole) are synthesized in methanol solution under physiological conditions. They are characterized by elemental analysis, IR, UV–Vis and X-ray crystallography. Structural analyses show that the vanadium atoms in complexes 1–5 are all in a distorted-octahedral environment with the N4O2 donor set, and intra- or inter-hydrogen bonding linkages have been also observed in each complex. Bromination reaction activity of the complexes has been evaluated by the method with phenol red as organic substrate in the presence of H2O2, Br− and phosphate buffer, indicating that they can be considered as potential functional model vanadium-dependent haloperoxidases. In addition, thermal analysis and quantum chemistry calculations were also performed and discussed in detail.