Showing papers by "Oscar E. Piro published in 2018"

Exploring weak intermolecular interactions in thiocyanate-bonded Zn(II) and Cd(II) complexes with methylimidazole: crystal structures, Hirshfeld surface analysis and luminescence properties

Abstract: Four new thiocyanate-Zn(II) and -Cd(II) complexes with 1-methylimidazole (1-MeIm) and 2-methylimidazole (2-MeIm), namely, Zn(1-MeIm)2(SCN)2 (1), Zn(2-MeIm)2(SCN)2 (2), Cd(1-MeIm)4(SCN)2 (3) and polymeric [Cd(2-MeIm)2(SCN)2]n (4), have been synthesized and characterized by IR, Raman and UV-Vis spectroscopy. The thermal behavior for all complexes was evaluated by thermo-gravimetric analysis and differential thermal analysis. The crystal structures of complexes 1–4 were solved by single-crystal X-ray diffraction methods. A study of intermolecular interactions in the solid state compounds revealed that molecules are linked by weak N–H⋯S and C–H⋯S hydrogen bonds and also by C–H⋯π interaction in the case of structures 2–4, which are responsible for the formation and stability of the molecular assemblies. Hirshfeld surfaces and 2D-fingerprint plots allowed us to visualize the intermolecular contacts and their relative contributions to the total surface for each compound. A comparative analysis against similar halogen-bonded complexes was carried out to investigate the tendency of inter-molecular interactions to form contacts in crystals by using the enrichment ratio descriptor. The emission spectra of the free imidazole derivatives and their Zn(II) and Cd(II) complexes were recorded in acetonitrile solutions. The emissions observed in the spectra of complexes were ascribed to the intra-ligand transitions and ligand-to-metal charge transfer and we have observed an interesting correlation between the fluorescence intensities and C–H⋯π interactions.

Crystal chemistry of organic minerals – salts of organic acids: the synthetic approach

Abstract: The term ‘organic minerals’ means naturally occurring crystalline organic compounds including metal salts of formic, acetic, citric, mellitic, methanesulfonic and oxalic acids. As for the rest of t...

Interaction of Zn with Losartan. Activation of Intrinsic Apoptotic Signaling Pathway in Lung Cancer Cells and Effects on Alkaline and Acid Phosphatases

Abstract: A new losartan [2-butyl-5-chloro-3-[[4-[2-(2H-tetrazol-5-yl)phenyl]phenyl]methyl]imidazol-4-yl]methanol zinc(II) complex [Zn(Los)Cl], was synthesized and characterized. The crystal structure was determined by x-ray diffraction methods. When aqueous solutions of the ligand and the metal were mixed, the known and more soluble powder [Zn(Los)2].3H2O (ZnLos) complex has been obtained. The interactions with phosphatases showed a concerted mechanism displayed by the Zn ions and ZnLos up to 500 μM concentration: a decrease of the acid phosphatase (AcP) associated with an increase in the alkaline phosphatase (ALP) activities. The complex and ZnSO4 showed a cytotoxic behavior on human lung A549 cancer cell line at concentrations higher than 75 μM with reactive oxygen species (ROS) generation and GSH (and GSH/GSSG ratio) depletion. Apoptotic cells were observed using terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) method, a mechanism accompanied by upregulation of BAX protein, downregulation of Bcl-XL and release of caspase-3. The BAX/Bcl-XL ratio was found to be significantly higher in cells exposure to ZnLos than cells treated with ZnSO4, in agreement with the higher apoptotic percentage of cells found for the complex. Cell death was found to be produced by apoptosis and no necrosis has been observed. On the contrary, losartan exerted low effects on phosphatases, produced some reduction of cancer cell viability (concentrations > 250 μM, number of apoptotic cells similar to the basal) with low ROS depletion, without alteration of the GSH/GSSG and low BAX/Bcl-XL ratios. In the MRC-5, normal lung fibroblasts cell line only ZnSO4 at concentrations higher than 200 μM displays cytotoxic effects.

Weak and strong hydrogen bonds conducting the supramolecular framework of 1-butyl-3-(1-naphthoyl)thiourea: crystal structure, vibrational studies, DFT methods, Pixel energies and Hirshfeld surface analysis

Abstract: A detailed structural and spectroscopic study of a new thiourea derivative 1-butyl-3-(1-naphthoyl)thiourea (1) is presented with the assistance of theoretical calculations. The X-ray diffraction structure analysis reveals a planar carbonylthiourea group, favoured by intra-molecular NH···O bond. The compound is arranged in the lattice as NH···O and NH···S bonded polymeric ribbons, that extend along the crystal b-axis. Molecular pairs involving N–H···S hydrogen bonds are a dominant contribution to packing stabilisation coming from coulombic component. Hirshfeld surfaces and two-dimensional-fingerprint plots show different intermolecular contacts and its relative contributions to total surface in each compound. The AIM approach shows the nature and strength of the strong and weak intramolecular interactions and the solvent effect, while NBO analysis reveals that the sulphur atom is responsible for the higher hyperconjugative stabilising energy.

Synthesis, characterization and crystal structure of 2-chloroethyl(methylsulfonyl)methanesulfonate

Abstract: The aim of this study was to evaluate the structural and vibrational properties and biological activity of 2-chloroethyl(methylsulfonyl)methanesulfonate, CH3SO2CH2SO2OCH2CH2Cl (clomesone). The solid-state molecular structure has been isolated and characterized using experimental (X-ray diffraction) and theoretical (DFT method) methodologies. The molecules are packed through C–H⋯O bifurcated interactions and Cl⋯Cl interactions. The experimental investigations are supplemented by quantum chemical calculations and Hirshfeld surface calculations. Furthermore, the infrared and Raman spectra of the solid phase have been obtained, and the observed bands are assigned to the vibrational normal modes. This study is completed using the atoms-in-molecules (AIM) theory and natural bond orbital (NBO) analysis. Finally, we studied the function of clomesone in biofilm formation and investigated a methanesulfonate complex with respect to QS activity.

Stability of the Monoelectronic Reduction Product from 1,2,5‐Thiadiazole S,S‐Dioxides. Electrochemical, Chemical, and Photoinduced Doping

Abstract: Fil: Caram, Jose Alberto. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - La Plata. Instituto de Investigaciones Fisicoquimicas Teoricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquimicas Teoricas y Aplicadas; Argentina

Crystallography and the liquid crystal phase: a new approach to structural studies on a thermo-tropic smectic Schiff base

Abstract: In spite of the apparent contradiction between ‘liquid crystals’ (LC, materials exhibiting some degree of disorder) and ‘crystallography’ (a paradigmatic ordered kingdom), X-ray diffraction (XRD) s...

Crystal structure and spectroscopic behavior of synthetic novgorodovaite Ca2(C2O4)Cl2·2H2O and its twinned triclinic heptahydrate analog

Abstract: Synthetic novgorodovaite analog Ca2(C2O4)Cl2·2H2O is identical to its natural counterpart. It crystallizes in the monoclinic I2/m space group with a = 6.9352(3), b = 7.3800(4), c = 7.4426(3) A, β = 94.303(4)°, V = 379.85(3) A3 and Z = 2. The heptahydrate analog, Ca2(C2O4)Cl2·7H2O, crystallizes as triclinic twins in the P $$\overline{1}$$ space group with a = 7.3928(8), b = 8.9925(4), c = 10.484(2) A, α = 84.070(7), β = 70.95(1), γ = 88.545(7)°, V = 655.3(1) A3 and Z = 2. The crystal packing of both calcium oxalate–chloride double salts favors the directional bonding of oxalate, C2O4 2−, ligands to calcium ions as do other related calcium oxalate minerals. The π-bonding between C and O atoms of the C2O4 2− oxalate group leaves sp 2-hydridised orbitals of the oxygen atoms available for bonding to Ca. Thus, the Ca–O bonds in both calcium oxalate–chloride double salts are directed so as to lie in the plane of the oxalate group. This behavior is reinforced by the short O···O distances between the oxygens attached to a given carbon atom, which favors them bonding to a shared Ca atom in bidentate fashion. Strong bonding in the plane of the oxalate anion and wide spacing perpendicular to that plane due to repulsion between oxalate π-electron clouds gives rise to a polymerized structural units which are common to both hydrates, explaining the nearly equal cell constants ~7.4 A which are defined by the periodicity of Ca-oxalate chains in the framework (monoclinic b ≈ triclinic a). When compared with novgorodovaite, the higher water content of Ca2(C2O4)Cl2·7H2O leads to some major differences in their structures and ensuing physical properties. While novgorodovaite has a three-dimensional framework structure, in the higher hydrate, the highly polar water molecules displace chloride ions from the calcium coordination sphere and surround them through OwH···Cl hydrogen bonds. As a result, polymerization in Ca2(C2O4)Cl2·7H2O solid is limited to the formation of two-dimensional Ca2(C2O4)(H2O)5 slabs parallel to (001), inter-layered with hydrated chloride anions. This layered structure accounts for (001) being both a perfect cleavage and a twin interface plane. The infrared and Raman spectra of both salts are also briefly discussed.

Structural and IR-spectroscopic characterization of pyridinium acesulfamate, a monoclinic twin

Abstract: Fil: Baran, Enrique Jose. Facultad de Ciencias Exactas, Universidad Nacional de la Plata; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - La Plata. Centro de Quimica Inorganica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Quimica Inorganica "Dr. Pedro J. Aymonino"; Argentina

Spontaneous enanti-omorphism in poly-phased alkaline salts of tris-(oxalato)ferrate(III): crystal structure of cubic NaRb5[Fe(C2O4)3]2.

Abstract: We show here that the phenomenon of spontaneous resolution of enanti­omers occurs during the crystallization of the sodium and rubidium double salts of the transition metal complex tris­(oxalato)ferrate(III), namely sodium penta­rubidium bis­[tris­(oxalato)ferrate(III)], NaRb5[Fe(C2O4)3]2. One enanti­omer of the salt crystallizes in the cubic space group P4332 with Z = 4 and a Flack absolute structure parameter x = −0.01 (1) and its chiral counterpart in the space group P4132 with x = −0.00 (1). All metal ions are at crystallographic special positions: the iron(III) ion is on a threefold axis, coordinated by three oxalate dianions in a propeller-like conformation. One of the two independent rubidium ions is on a twofold axis in an eightfold coordination with neighbouring oxalate oxygen atoms, and the other one on a threefold axis in a sixfold RbO6 coordination. The sodium ion is at a site of D3 point group symmetry in a trigonal–anti­prismatic NaO6 coordination.