Showing papers by "Mariana Mitewa published in 2008"

First divalent metal complexes of the polyether ionophore Monensin A: X-Ray structures of [Co(Mon)2(H2O)2] and [Mn(Mon)2(H2O)2] and their bactericidal properties.

Abstract: The complexation of carboxylic acid Monensin A (MonH, 1a) with CoCl2.6H2O and MnCl2.4H2O leads to the formation of mononuclear complexes [Co(Mon)2(H2O)2], 2a and [Mn(Mon)2(H2O)2], 2b, respectively. The unique crystal structures of 2a and 2b were determined by X-ray crystallography. The complexes crystallize in the monoclinic space group P21 with an octahedrally coordinated transition metal center forming the crystallographically centrosymmetric chromophore CoO6 or MnO6, respectively. Two molecules of Monensin A act bidentately through their carboxylate moiety and a hydroxyl group, and two water molecules are additionally transcoordinated. Although the transition metal ions are not bound into the cavity of the ligand, the unusual bidentate coordination mode of the ionophore induces its “pseudo-cyclization” forming 22-membered cycles further stabilized by a number of H-bonds. The complexes are the first example of divalent metal complexes of the monovalent polyether ionophore. The parallel study on the complexation ability of the potassium complex of Monensin A (MonK, 1b) towards Co(II) and Mn(II) showed the formation of the isostructural complexes 2a and 2b accompanied by loss of the potassium ion due to the new coordination mode of the ligand. The biological tests performed with the antibiotic MonH and the corresponding metal(II) complexes show greatly enhanced antimicrobial activity of complexes 2a-b against Gram(+)-bacteria.

Detection and identification of atypical quetiapine metabolite in urine

Abstract: Quetiapine fumarate (Seroquel®) is an atypical antipsychotic dibenzothiazepine derivative. Due to its extensive hepatic metabolism and low level of unchanged excretion (< 1%) the routine toxicological drug-screening analyses of urine often leads to false negative results. In the present study, we report that a newly identified metabolite of quetiapine, N-desalkylquetiapine, can be used as an indicative marker of quetiapine-intake in urine using common GC-MS screening procedure. The structure of the mentioned metabolite was solved from the mass-spectrum obtained and the quetiapine presence was proved by consequent HPLC plasma analysis.

X-ray structure and magnetochemical study on a Co(II) complex of 2-acetyl-1,3-indandione

Abstract: An X-ray structure of a Co(II) complex of bidentate chelating 2-acetyl-1,3-indandione (2AID) is reported–Co(2AID)2(H2O)2 · 2H2O. The compound crystallizes in the monoclinic space group P21/n with four molecules per unit cell. The molecular structure shows distorted octahedral geometry of the metal center. The complex is characterized by EPR and magnetic measurements, which show high-spin electronic structure for the metal ion.

Ab initio and DFT study of the structure of metal ion complexes with N-benzalaniline-15-crown-5

Abstract: The structures of N-(4-benzalaniline)-15-crown-5 and N-(4'-benzalaniline)-15-crown-5 and their Li + , Na + , K + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ complexes are optimized using ab initio and DFT methods. It was found that in all cases the M n+ ―N distances (n = 1, 2) are longer than the average M n+ ―O ones in the corresponding complexes and the metal― nitrogen distances in the alkali metal complexes are longer than these in alkaline earth ones. The Li + , Na + , Mg 2+ and Ca 2+ cations fit to cavity size of the crown while the K + , Sr 2+ and Ba 2+ cations, whose size is greater than the diameter of the macrocycle cavity, protrude from the macrocycle. In all cases the conformation of the crown ether does not change except the Be 2+ complex, where the conformation of the macrocycle is strongly deformed.