Showing papers by "Enrique J. Baran published in 2004"

New Vanadium(V) Complexes with Salicylaldehyde Semicarbazone Derivatives: Synthesis, Characterization, and in vitro Insulin-Mimetic Activity − Crystal Structure of [VvO2(salicylaldehyde semicarbazone)]

Abstract: The new dioxo(semicarbazone)vanadium(V) complexes cis-VO2L, where L = salicylaldehyde semicarbazone (L1), salicylaldehyde 4-n-butylsemicarbazone (L2), or salicylaldehyde 4-(2-naphthyl)semicarbazone (L3), have been synthesized, characterized by 1H and 13C NMR and FTIR spectroscopy and tested for bioactivity as potential insulin-mimetic agents. All dioxovanadium(V) complexes exhibited essentially no in vitro insulin-mimetic activity, but the VO2L2 complex developed activity in the presence of ascorbic acid, similar to that of vanadyl sulfate. The molecular structure of the novel complex VO2L1 has been solved by X-ray diffraction methods. It crystallizes in the tetragonal space group P42/n with a = 12.7674(7), c = 11.5308(5) A, and Z = 8. The vanadium atom is in a distorted square-pyramidal coordination, with L1 acting as a tridentate ligand through its azomethyne nitrogen atom, carbonyl oxygen atom and deprotonated phenol oxygen atom. The coordination sphere is completed by two oxo ligands at cis positions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Characterization of two new zinc(II) complexes with saccharinate and imidazole or benzimidazole as ligands

Abstract: The crystal structure of the complexes [Zn(sac)2(im)2] (1) and [Zn(sac)2(bzim)2]2⋅2Et-OH⋅H2O (2) (sac = saccharinate anion; im = imidazole; bzim = benzimidazole; EtOH = ethanol) was determined by single crystal X-ray diffractometry. Complex 1 crystallizes in the monoclinic P2 1/n space group with a = 9.1585(5), b = 16.4409(6), c = 15.0249(5) A, β = 94.079(1)°, and Z = 4, whereas complex 2 belongs to the triclinic space group P1 with a = 10.8500(2), b = 12.4860(2), c = 13.5640(3) A, α = 115,696(1), β = 100.086(1), γ = 102.169(1)°, and Z = 1. In both complexes, the Zn(II) cations are in a slightly distorted tetrahedral ZnN4 environment, coordinated to two saccharinate anions and to two imidazole (1) and to two benzimidazole (2) molecules. The complexes were also characterized by means of infrared spectroscopy and their thermal behavior investigated by means of thermogravimetric and differential thermal analytical techniques.

Preparation and characterization of dimercury(I) monofluorophosphate(V), Hg2PO3F: crystal structure, thermal behavior, vibrational spectra, and solid-state 31P and 19F NMR spectra.

Abstract: Single crystals of anhydrous dimercury(I) monofluorophosphate(V), Hg(2)PO(3)F (1), were obtained by cooling diluted aqueous Hg(2)(NO(3))(2) and (NH(4))(2)PO(3)F solutions from 85 degrees C to room temperature. Compound 1 crystallizes with eight formula units in the orthorhombic space group Ibam (No. 72) and lattice parameters a = 9.406(2) A, b = 12.145(3) A, c = 8.567(2) A. It adopts a new structure type even though a topological relation with dimercury(I) sulfate, Hg(2)SO(4), is established. The crystal structure of 1 (R(F(2) > 2sigma(F(2)) = 0.0353) exhibits Hg(2)(2+) dumbbells and discrete PO(3)F(2)(-) anions as single building units which are organized in a layered assembly parallel to (100). The symmetric Hg(2)(2+) dumbbell shows a typical Hg-Hg distance of 2.5051(9) A, and for each Hg atom, three Hg-O distances are found, ranging from 2.327(6) to 2.476(5) A. No interactions between Hg and F atoms are realized. The latter is exclusively bonded to the phosphorus atom at a distance d(P-F) = 1.568(8) A which is considerably longer than the P-O distances with a mean of 1.515 A. Compound 1 was further characterized by vibrational spectroscopy (Raman and IR) in the spectral range between 4000 and 50 cm(-)(1), thermal analysis (TG, DSC) up to 650 degrees C which revealed Hg(2)(P(2)O(7)) and Hg(3)(PO(4))(2) as thermal decomposition products, and (19)F and (31)P solid-state NMR spectroscopy. The value for the P-F coupling constant in 1 is J(PF) = -1072 Hz at 20 degrees C. The absolute sign of J(PF) is negative.

The reversible α → β phase transition of Cu2As2O7

Abstract: Single crystals of copper(II) pyroarsenate(V), Cu2As2O7, were prepared by chemical transport reactions in sealed and evacuated silica ampules starting from stoichiometric mixtures of the component oxides and chlorine as transport agent (temperature gradient 880 → 800 °C, 5 days). Cu2As2O7 is dimorphous and shows a reversible α (low-temperature) ↔ β (high-temperature) phase transition at 356(2) °C detected by differential scanning calorimetry (DSC) and high-temperature X-ray powder diffraction (XRPD) measurements. The crystal structure of α-Cu2As2O7 (C2/c, Z = 4, a = 7.237(3), b = 8.2557(17), c = 9.780(3) A, β = 111.03(2)°, R[F2 > 2σ(F2)] = 0.028) was determined from single-crystal data at room temperature. It crystallizes isotypically with α-Cu2P2O7 and β-Cu2V2O7. The thortveitite-type crystal structure of β-Cu2As2O7 (C2/m, Z = 2, a = 7.0987(3), b = 8.2777(4), c = 4.8666(2) A, β = 110.206(4)°, R(Bragg) = 0.1056) was determined by means of high-temperature XRPD recorded at 400 °C. The crystal structures of...

Spectroscopic and Magnetic Behaviour of the Copper (II) Complex of L-Tryptophan

Abstract: SUMMARY. A copper(II) complex of the amino acid L-tryptophan, of stroichiometry Cu(Trp)2, was obtained from aqueous solution. Its structural characteristics were deduced from the careful analysis of infrared, Raman and electronic absorption spectra, complemented with magnetic susceptibility measurements in the temperature range between 2 and 300 K. The metal center presents a distorted octahedral CuN2O4 environment with a trans arrangement of the amino acids in the equatorial plane, involving the terminal amino and carboxylate groups. The coordination sphere is complemented with two longer apical Cu-O bonds involving “free” O-carboxylato atoms of neighboring complex moieties. RESUMEN. “ Comportamiento Espectrosco pico y Magne tico del Complejo de Cobre (II) con L-Triptofano ” . Un complejo de cobre (II) con el amino acido L-triptofano, de estequiometr ia Cu(Trp)2, fue obtenido de solucio n acuosa. Sus caracteristicas estructurales fueron deducidas en base a un pormenorizado an alisis de sus espectros de infrarrojo, Raman y de absorcio n electro nica, complementado con medidas de susceptibilidad magne tica en el intervalo de temperaturas entre 2 y 300 K. El centro met alico presenta un entorno CuN2O4 octae drico distorsionado con una disposicio n trans de los amino acidos en el plano ecuatorial, involucrando los grupos amino y carboxilato terminales. La esfera de coordinaci o n se complementa con dos enlaces Cu-O axiales mas largos, involucrando atomos de oxigeno “ libres” de grupos carboxilato de unidades complejas vecinas.

Vibrational spectra of some pharmacologically interesting pyroglutamato complexes

Abstract: The infrared and Raman spectra of lithium, zinc, calcium and magnesium complexes of L-pyroglutamic acid were recorded and are briefly discussed. For the first three compounds the spectral discussion is based on their known structural characteristics. Comparing the spectroscopic behaviour of the complexes and the free acid, some comments on the structural peculiarities of the magnesium compound could be advanced. The pharmacological interest of these complexes is also briefly discussed. Copyright © 2004 John Wiley & Sons, Ltd.

Vibrational spectra of Cd2As2O7

Abstract: The infrared and Raman spectra of Cd2As2O7, belonging to the thortveitite structural type, were recorded and are discussed on the basis of a factor group analysis and by comparisons with related compounds. Copyright © 2004 John Wiley & Sons, Ltd.

Vibrational properties of hydrogen astatide, HAt

Abstract: A number of theoretical studies on the bond characteristics of HAt, the heaviest hydrogen halide, have recently been reported On the basis of these data the force constant, mean amplitudes of vibration and thermodynamic functions of this molecule have been calculated Some comparisons with the related lighter hydracids are made

Mean Amplitudes of Vibration of the trans-IO2F4 – Anion

Abstract: The mean amplitudes of vibration of the trans-IO 2 F 4 - anion have been calculated from known spectroscopic data between 0 and 1000 K. Bond peculiarities are discussed in comparison with those of trans-IO 2 F 5 2 - and of some other structurally related species.