Showing papers by "Oscar E. Piro published in 2000"

X-ray diffraction study of copper(I) thiourea complexes formed in sulfate-containing acid solutions

Abstract: The formation of three different copper(I) thiourea complexes in sulfate-containing acid solutions was observed. The ratio between CuI and thiourea (tu) in these complexes depends on the amount of thiourea and copper sulfate in the solution. The crystal and molecular structure of a new complex, [Cu_2(tu)_6](SO_4)\cdotH_2O, was determined, and the formation and structures of [Cu_2(tu)_5](SO_4)\cdot3H_2O and [Cu_4(tu)_7](SO_4)_2\cdotH_2O were confirmed. The compound [Cu_2(tu)_6](SO_4)\cdotH_2O crystallizes in the P\overline 1 space group, with a = 11.079 (2), b = 11.262 (1), c = 12.195 (2) A, \alpha = 64.84 (1), \beta = 76.12 (1), \gamma = 66.06 (1)°, and Z = 2. The Cu-thiourea complex is arranged as a CuI tetranuclear ion, [Cu_4(tu)_{12}]^{4+}, sited on a crystallographic inversion center. All copper ions are in a tetrahedral coordination with thiourea ligands and located at alternate sites on an eight-membered, crown-like ring.

Structural and Spectroscopic Characterization of Two New Cu(II)-Dipeptide Complexes

Abstract: Two new Cu(II) complexes of stoichiometry [Cu(L-dipept)], containing as ligands the dipeptides L-alanine-L-valine and L-alanine-L-phenylalanine were prepared. They were characterized by single crystal X-ray diffractometry, and infrared and electronic spectroscopy. Both crystallize in the orthorhombic space group P212121 with Z = 4. The Cu(II) ion has essentially the same elongated pyramidal coordination, being equatorially cis coordinated by a N2O2 arrangement of ligand atoms and axially by a carbonyl oxygen atom. The compounds show rather similar polymeric structures that differ from each other basically in the dihedral angle between adjacent N2O2 planes. The infrared and electronic spectra are briefly discussed on the basis of the structural characteristics of the complexes. Superoxide dismutase-like activity was tested for both compounds.

Synthesis, structure and magnetic properties of tetrakis-μ-carboxylato-bis(dodecylnicotinato)dicopper(II) complexes; crystal and molecular structure of the decyl carboxylate derivative

Abstract: Dodecylnicotinate bis-adducts of binuclear copper carboxy­lates, of the general formula Cu2(O2CCn − 1H2n − 1)4(C5H4N­COOC12H25)2, were synthesized for n = 10, 12, 14, 16, 18 and 20, and their crystal structure, thermal behavior and magnetic properties studied The molecular structure of the decyl derivative has been determined from single-crystal X-ray diffraction data The dimer is centrosymmetric with the CuII ions in a square-pyramidal coordination with four O-alkyl O atoms [average d(Cu—O) 1960 (6) A] in the basal plane and the nicotine N atom at apical positions [d(Cu—N) 2183 (3) A] The copper ions, 2615 (1) A apart, are bridged by four O-alkyl carboxylate groups Both the n = 20 and n = 18 homologues exhibit lamellar phases, which can be related to the supramolecular arrangement found in the n = 10 derivative The magnetic behavior of the decyl and octadecyl dimers was studied in the 2–300 K temperature range They exhibit a strong intramolecular antiferromagnetic interaction (Cu–Cu superexchange coupling constant J = −347 cm−1 for the decyl derivative), which can be attributed to a large overlap of the metal 3d orbitals and the oxygen lone pair orbitals of the linking carboxylate groups

Structural and spectroscopic characterization of tris (o-phenanthroline)iron(II) disaccharinate monosaccharin hexahydrate

Abstract: The crystal and molecular structure of the title compound, for short [Fe(o-phen)3](sac)2·(Hsac)·6H2O, has been determined by X-ray diffraction methods. It crystallizes in the monoclinic space group P21/n with a = 16.3190(1), b = 19.2890(1), c = 17.4490(2) A, β = 92.586(1)°, V = 5486.95(8) A3 and, Z = 4. The investigated compound constitutes the first example of a species in which uncoordinated saccharin and saccharinate anions are present in the structure. The crystallographic results reveal the subtle differences between the structure of the neutral molecule and its anion. The complex was also characterized by means of infrared, electronic, and 57Fe-Mossbauer spectroscopy. Its magnetic susceptibility was determined at room temperature and its thermal behavior investigated by means of thermogravimetric and differential thermal analytical techniques.

Addition of Aromatic Nucleophiles to a C=N Double Bond of 1,2,5-Thiadiazole 1,1-Dioxide

Abstract: A new synthesis of 3,4-diphenyl-4-aryl-1,2,5-thiadiazolines 1,1-dioxide through the addition of aromatic derivatives to 1,2,5-thiadiazole 1,1-dioxide is presented. Anhydrous AlCl3 is used as catalyst.