Crystal structures, spectroscopic characterization and theoretical calculations of the guanidinium and ammonium salts of the insulin-enhancing anion [VO2(dipic)]−

The novel complex, C(NH2)3[VO2(dipic)] · 2H2O (1), and its analogous, NH4[VO2(dipic)] (2), were synthesized and characterized in the solid state by means of FT-Raman and FT-infrared spectroscopies. Their crystal and molecular structures were determined by X-ray diffraction methods. The optimized geometry of the [VO2(dipic)]− anion and its corresponding harmonic vibrational frequencies were calculated using methods of the density functional theory. The [VO2(dipic)]− anion in both salts show a similar penta-coordinated environment. The planar dipic2− ligand coordinates to the VO2+ moiety through one oxygen of each carboxylate and the nitrogen atom. Slight but significant differences between the bonding structures in both compounds were observed. The crystal structures are stabilized by hydrogen bridging interactions.

Graphical abstractThe guanidinium and ammonium salts of the bisoxodipicolinatevanadate(V) anion were synthesized and characterized by single-crystal X-ray diffraction and spectroscopic techniques. The optimized geometry of [VO2(dipic)]− and its corresponding harmonic vibrational frequencies were calculated using methods of the density functional theory. Hydrogen bonding interactions appear to be relevant in stabilizing their crystal structures.Figure optionsDownload full-size imageDownload as PowerPoint slide