NMR study on the coordination of diperoxovanadium(V) complexes with 2-hydroxymethyl pyridine derivatives

<p>To understand the substitution effects of 2-hydroxymethyl pyridine on the reaction equilibrium, the interactions between a series of 2-hydroxymethyl pyridine derivatives and diperoxovanadium(V) complex [OV(O<sub>2</sub>)<sub>2</sub>(D<sub>2</sub>O)]<sup>−</sup>/[OV(O<sub>2</sub>)<sub>2</sub>(HOD)]<sup>−</sup> in solution were explored by the combined use of multinuclear (<sup>1</sup>H, <sup>13</sup>C, and <sup>51</sup>V) magnetic resonance together with HSQC in 0.15 mol L<sup>−1</sup> NaCl ionic medium for mimicking the physiological conditions. Some direct NMR data are given for the first time. The relative reactivity among the 2-hydroxymethyl pyridine ligands is 2-hydroxymethyl pyridine (<b>1</b>) > 2-methoxymethyl pyridine (<b>2</b>) > 2-ethoxymethyl pyridine (<b>3</b>) > 2-propoxymethyl pyridine (<b>4</b>). The competitive coordination results in the formation of a series of new seven-coordinate diperoxovanadium species [OV(O<sub>2</sub>)<sub>2</sub>L]<sup>–</sup> (L = <b>1</b>, <b>2</b>, <b>3</b>, and <b>4</b>). The results of density functional calculations indicated that steric effects play an important role in these reactions, providing a reasonable explanation on the relative reactivity of the 2-hydroxymethyl pyridine derivative.</p>