title: NMR and theoretical study on interactions between diperoxovanadate complex and pyrazole-like ligands.
abstract: To understand the effects of pyrazole substitution on reaction equilibrium, the interactions between a series of pyrazole-like ligands and [OV(O(2))(2)(D(2)O)](-)/[OV(O(2))(2)(HOD)](-) were explored by using multinuclear ((1)H, (13)C, and (51)V) magnetic resonance, HSQC, and variable temperature NMR in 0.15 mol/L NaCl ionic medium mimicking physiological conditions. These results show that the relative reactivities among the pyrazole-like ligands are 3-methyl-1H-pyrazole approximately 4-methyl-1H-pyrazole approximately 1H-pyrazole>1-methyl-1H-pyrazole. As a result, the main factor which affects the reaction equilibrium is the steric effect instead of the electronic effect of the methyl group of these ligands. A pair of isomers has been formed resulting from the coordination of 3-methyl-1H-pyrazole and a vanadium complex, which is attributed to different types of coordination between the vanadium atom and the ligands. Thus, the competitive coordination leads to the formation of a series of six-coordinate peroxovanadate species [OV(O(2))(2)L](-) (L, pyrazole-like ligands). Moreover, the results of density functional calculations provided a reasonable explanation on the relative reactivity of the pyrazole-like ligands as well as the important role of solvation in these reactions.
authors.affiliation: Key Laboratory of Theoretical Chemistry and Molecular Simulation of Ministry of Education, School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan, Hunan, China.
authors.forename: Xianyong
authors.initials: X
authors.lastname: Yu
authors.forename: Ronghua
authors.initials: R
authors.lastname: Liu
authors.forename: Hongliang
authors.initials: H
authors.lastname: Peng
authors.forename: Haowen
authors.initials: H
authors.lastname: Huang
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Li
authors.forename: Baishu
authors.initials: B
authors.lastname: Zheng
authors.forename: Pinggui
authors.initials: P
authors.lastname: Yi
authors.forename: Zhong
authors.initials: Z
authors.lastname: Chen
mesh_terms: D008024:Ligands; D008962:Models, Theoretical; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D010545:Peroxides / Q000737:chemistry*; D011720:Pyrazoles / Q000737:chemistry*; D014638:Vanadates / Q000737:chemistry*
chemical_list: D008024:Ligands; D010545:Peroxides; D011720:Pyrazoles; C091767:diperoxovanadate; D014638:Vanadates