Crystal structure, NMR and catalytic properties of a bis-peroxovanadium [NH₄][VO(O₂)₂(mpa)]·H₂O

Abstract

By reacting NH₄VO₃ and mpa (mpa = 4-methoxypicolinamide) in the presence of H₂O₂, a bis-peroxovanadium [NH₄][VO(O₂)₂(mpa)]·H₂O (1) was obtained and characterized by X-ray single-crystal diffraction. Structural analyses demonstrate that 1 belongs to the monoclinic space group P2₁/c and consists of a bis-peroxovanadium [VO(O₂)₂(mpa)]⁻, one NH₄⁺ counterion and one free lattice water. Adjacent [VO(O₂)₂(mpa)]⁻ anions construct a 3D supramolecular framework through intra- and intermolecular hydrogen bonding interactions. The compositions of 1 in solution are investigated by using multinuclear (¹H, ¹³C, and ⁵¹V) magnetic resonance, COSY, HSQC, HMBC, and variable temperature NMR in a 0.15 mol L⁻¹ NaCl/D₂O solution that mimics the physiological conditions. Comparing the results of single-crystal X-ray and NMR experiments, the V^V ion in the undissociated [VO(O₂)₂(mpa)]⁻ in solution displays a similar seven-coordinate distorted pentagonal bipyramidal geometry with the solid-state crystal. The catalytic activity of the 1 in the oxidative bromination for phenol/aniline-like compounds to mimic bromoperoxidases reactivity was also studied.

Graphical Abstract

Keywords:

• NMR
• bis-peroxovanadium
• crystal structure
• supramolecular framework
• catalysis

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (21601058) and the Hunan Provincial Natural Science Foundation of China (2018JJ3146).