Preparation, Structural and Spectroscopic Characterization of Vanadium(IV) and Vanadium(V) Complexes with Dipicolinic Acid

The reaction of dipicolinic acid, dipicH2, with vanadyl sulfate in the mixture of ethanol and water led to the formation of[VO(dipic)(H2O)2].C2H5OH (1) and [VO(dipic)(H2O)(OC2H5)] (2). Complex 1 was obtained first and complex 2 after prolonged standing of the mother liquor in air. Both complexes were characterized by elemental analyses, IR, Raman and UV/Vis spectroscopic analyses and their structures were determined by X-ray diffraction. The vanadium(IV) ion in 1 and vanadium(V) ion in 2 are both coordinated by the O,N,O'-tridentate dipicolinate ligand. The octahedral coordination of the vanadium(IV) atom is completed by two water molecules in trans position and by an oxo oxygen atom, whereas the vanadium(V) atom is additionally coordinated by an oxo oxygen atom and a water molecule in trans position and by an ethoxido oxygen atom. A co-crystallized ethanol molecule is also present in the crystal structure of 1. Molecules of [VO(dipic)(H2O)2] and ethanol are linked into a 2D network by the O-H...O hydrogen bonds in the structure of 1. Molecules of 2 are assembled into a 3D structure by the O-H...O hydrogen bonds.