Crystal structures, spectroscopic characterization and theoretical calculations of the guanidinium and ammonium salts of the insulin-enhancing anion [VO 2(dipic)] −

Abstract

The novel complex, C(NH 2) 3[VO 2(dipic)] · 2H 2O ( 1), and its analogous, NH 4[VO 2(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 [VO 2(dipic)] − anion and its corresponding harmonic vibrational frequencies were calculated using methods of the density functional theory. The [VO 2(dipic)] − anion in both salts show a similar penta-coordinated environment. The planar dipic 2− ligand coordinates to the VO 2 + 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.