Effect of Pr-Ca substitution on the transport and magnetic behavior of LaMnO3 perovskite

The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO₃ perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good example of these properties is (La_1−2x Pr _x Ca _x )MnO₃ (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T _c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for understanding the structural, transport and magnetic properties are discussed in detail.     

Crystal Structures of Analogs of threo-Methylphenidate

The crystal structures of the chloride salts of five analogs of threo-methylphenidate have been obtained. Four of these have different substituents on the phenyl ring while the fifth is the ethyl ester of methylphenidate. All five structures have similar three-dimensional conformations and these are compared with the global minimum obtained by MM2-87 calculations. There is good agreement between the crystal structures and the computed global minimum with the major difference being the presence of a chloride counterion in the crystal structures that prevents the carbonyl oxygen from approaching the equatorial ammonium hydrogen as closely as in the computed global minimum.     

Crystal structure of [RuCl2[N-(2,4,6-trimethyl-benzyl)N-(n-butyl)]-imidazolidin-2-ylidene] and [RuCl2[N-(2,4,6-trimethyl-benzyl)-N-(2-methoxyethyl)]-imidazolidin-2-ylidene]

Two imidazolidin ruthenium complexes, [RuCl₂{[N-(2,4,6-trimethyl-benzyl)-N-(n-butyl)]-imidazolidin-2-ylidene}], 1, and [RuCl₂{[N-(2,4,6-trimethyl-benzyl)-N-(2-methoxyethyl)]-imidazolidin-2-ylidene}], 2, have been synthesised and their crystal structures have been determined from single crystal X-ray diffraction data. Compound 1 is monoclinic, of space group C2/c with a = 18.466(4) Å, b = 14.816(3) Å, c = 15.413(3) Å, β = 118.067(2)^∘, and V = 3720.9(12) ų with Z = 8 for d_calc = 1.536 g/cm³. Compound 2 is monoclinic, of space group P2₁/c with a = 8.1800(5) Å, b = 14.344(8) Å, c = 14.809(9), β = 91.604(10)^∘, and V = 1736.7(18) ų with Z = 4 for d_calc = 1.653 g/cm³. In each complex the ligand functions as an arene and carbene, occupying four coordination sites. The two chlorines in each compound complete a distorted octahedron.     

Heavy metal complexes of macrocyclic trithioethers

We report here two crystal structures of heavy metal complexes containing macrocyclic trithioethers. The trithioether, 10S3 (1,4,7-trithiacyclodecane) complexes Pb(II) to form a compound of the formula [Pb(10S3)](ClO₄)₂(H₂O) (Compound 1). This behavior contrasts the related trithioether 9S3 (1,4,7-trithianonane), which readily forms a bis Pb(II) complex. Crystals of Compound 1 consist of [Pb(10S3)(H₂O)]²⁺ units and perchlorate anions which are weakly bound to the Pb²⁺ center. The two perchlorate anions serve as bidentate ligands to a single lead(II) center. However, a third oxygen in one of the perchlorates also serves as a bridging group between two lead(II) centers, linking the [Pb(10S3)(H₂O)]²⁺ units into zigzag chains. Thus, a highly irregular nine-coordinate (S₃O₆) environment around the Pb²⁺ion is formed by the three sulfur donors from the 10S3 ligand, one coordinated water, and five oxygens from three different perchlorate anions. Also, the lone pair electrons on the Pb center are stereochemically active. Compound 2, [Cd(9S3)₂](ClO₄)₂ 2 CH₃NO₂, forms a distorted octahedral structure with unusual hexakis(thioether) coordination to the Cd(II) center. Bond distances and angles are very comparable to those found in the structure of the tetrafluoroborate salt of the complex cation. (1): P2₁/c, a = 9.1720(6) Å, b = 15.7687(11) Å, c = 11.8427(8) Å, = 93.0180(10) , V = 1710.4 (2) ų, Z = 4; (2): P2₁/c , a = 10.4305(10) Å, b = 15.2059(6) Å, c = 9.4919(7) Å, = 99.324(9), V = 1485.6(2) ų, Z = 2.     

The Preparation, Characterization and X-ray Structural Analysis of Tetrakis[1-Methyl-3-(2-Propyl)-2(3H)-Imidazolethione]Cadmium(II) Hexafluorophosphate

Abstract  A new compound, [Cd(mipit)₄][PF₆]₂ has been synthesized and characterized via standard solid and solution state methods including single crystal X-ray crystallography (mipit = 1-methyl-3-(2-propyl)-2(3H)-imidazolethione). The title compound crystallizes in tetragonal space group I4 ₁ /a with a = 12.478(2) ?, b = 12.478(2) ?, c = 28.806(6) ?, and Z = 4. The complex is a high melting, colorless solid that has a distorted tetrahedral CdS₄ coordination geometry. Thermogravimetric analysis results for the title compound as well as for another potential CdS synthon and two potential CdSe synthons are reported. Graphical Abstract  The synthesis and characterization of the title compound, a new ionic homoleptic cadmium complex, tetrakis[1-methyl-3-(2-propyl)-2(3H)-imidazolethione]cadmium(II) hexafluorophosphate is reported. The results of a single crystal X-ray diffraction analysis reveal a distorted tetrahedral CdS₄ coordination sphere about the cadmium. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.