Molecular, supramolecular and solution structures of peroxovanadium complexes with ON and O3N donor set ligands: two new types of cationic-anionic peroxovanadium(V) peroxovanadates(V)

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Authors	MAĎAROVÁ M. SIVÁK M. KUCHTA L. MAREK Jaromír BENKO J.
Year of publication	2004
Type	Article in Periodical
Magazine / Source	Dalton transactions : an international journal of organic chemistry
MU Faculty or unit	Faculty of Science
Citation
Field	Inorganic chemistry
Keywords	vanadium (V); peroxo complexes; X-ray structure; hydrogen bonds; NMR spectroscopy
Description	The complexes, [VO(O-2)(pa)(2)] ClO4 . 3H(2)O ( 1), [VO(O-2)(pa)(2)][ VO(O-2)(2)(pa)] . 3H(2)O (2), [VO(O-2)(pa)(2)][VO(O-2)( ada)] . 2H(2)O ( 3) and [VO(O-2)(pa)(pca)] . H2O ( 4) [pa = picolinamide, ada = carbamoylmethyliminodiacetate( 2-) and pca = 2- pyrazinecarboxylate(1-)], were synthesized. 2 and 3 are new types of peroxovanadium complexes: monoperoxovanadium diperoxovanadate ( 2) and monoperoxovanadium monoperoxovanadate ( 3). The complexes were characterized by chemical analysis and IR spectroscopy, and 1, 3 and 4 also by X-ray analysis. The structure of 1 is disordered, with alternating positions of the oxo and peroxo ligands. The peroxo oxygen atoms, O-p, in 1 are involved in weak hydrogen bonds with water molecules and close intramolecular C - H...O-p bonds [d(H...O-p) similar to 2.0 Angstrom]. The supramolecular structure of 1 is formed by a network of hydrogen bonds and strong attractive intermolecular pi - pi interactions between the pyridine rings. The supramolecular architecture in 4 is constructed by (N, O) - H...O hydrogen bonds between the neutral complex molecules and water of crystallization. The peroxo oxygen atoms in 4 form intramolecular C - H...O-p bonds [d( H...O-p) = 2.303 Angstrom]. The pa and pca ligands are ON coordinated via the oxygen atoms of the C(NH2)=O and COO- groups, respectively, and nitrogen atoms of the heterocyclic rings, and ada as a tetradentate O3N ligand. The thermal analysis of 4 showed that the loss of water of crystallization and the active oxygen release (T-min/degreesC 82, T-max/degreesC 165) are, under given conditions, individual processes separated by the temperature interval 90 - 132 degreesC. The solution structures and stability were studied by UV-VIS and V-51 NMR spectroscopies.
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