NMR and theoretical study on the linking properties of peroxovanadium(V) complexes with the 2-acylpyridine derivatives

To understand the substitution effects of 2-acylpyridine on the reaction equilibrium, the coordination interaction between a series of 2-acylpyridine derivatives and peroxovanadium(V) complex [OV(O-2)(2)(D2O)](-)/[OV(O-2)(2)(HOD)](-)in solution was explored by the combined use of multinuclear (H-1,C-13, and(51)V) magnetic resonance, COSY, together with HSQC in 0.15 M NaCl ionic medium for mimicking the physiological conditions. Some direct NMR data are given for the first time. The relative reactivity among the 2-acylpyridine derivative ligands is 2-acetylpyridine (1) > 2-propionylpyridine (2) > 2-butyrylpyridine (4) > 2-isobutyrylpyridine (3). The competitive coordination results in the formation of a series of new seven-coordinate peroxovanadium species [OV(O-2)(2)L](-)(L = 1,2,3, and4). The results of density functional calculations indicated that the solvation effects play an important role in these reactions, providing a reasonable explanation on the relative reactivity of the 2-acylpyridine derivative.