Novel vanadium complexes with rigid carboxylate ligands: Synthesis, structure and catalytic bromine dynamics of phenol red

In this work, by selecting appropriate ligands, novel vanadium complexes [(VO)-O-IV(2,6-pdc)(Phen)]center dot 3H(2)O (1) and [((VO)-O-IV)(C5H5N2O2)center dot 2H(2)O]center dot 2H(2)O (2) (2,6-pdc = 2,6-pyridinedicarboxylic acid, Phen = 1,10-Phenanthroline monohydrate) were synthesized by the reaction of V-2(SO4)(3), 2,6-pdc and Phen (for 1), VO(acac)2 and C5H6N2O2 (for 2) via solution or hydrothermal methods. Two complexes were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TG), UV-vis spectroscopy and the single crystal X-ray diffraction. Structural analyses reveal that the vanadium atom has distorted octahedral geometry in 1 and 2 with donor sets of N3O3 and N2O4, respectively. The complexes which catalyze the oxidation of the organic substrate phenol red in the presence of H2O2 and bromide exhibited catalytic bromination activity, and the reaction system is considered as an effective model for hydrogen peroxide determination. The reaction rate constant (k) for complexes 1 and 2 can be calculated as 2.13 x 10(2) and 2.64 x 10(2) (mol/L)(-2)s(-1), respectively. (C) 2017 Elsevier B.V. All rights reserved.