Showing papers by "Milan Melnik published in 2006"

New dimeric copper(II) complex [Cu(5-MeOsal)2(μ-nia)(H2O)]2 with magnetic exchange interactions through H-bonds

Abstract: The synthesis and characterization (elemental analysis, IR, electronic and EPR spectra as well as magnetization measurements over the temperature range 18 K–300 K) of solid complex [Cu(5-MeOsal)2(μ-nia)(H2O)]2 (1; 5-MeOsal = 5-methoxysalicylate, nia = nicotinamide) is reported together with the crystal structure In blue–green complex 1, two Cu(5-MeOsal)2(H2O) units are held together by a pair of bidentate nonchelating nicotinamide ligands, which form a (CuNC3O)2 ring Each Cu atom adopts a distorted square-pyramidal geometry The oxygen atoms from two unidentate 5-MeOsal anions occupy the trans position, a water molecule and the pyridine N atom of nicotinamide build the basal plane and a carboxamide O atom occupies the apical position The separation between two Cu atoms within the centrosymmetric dimer is 6940(2) A The dimeric units are self-assembled across a centre of symmetry by the formation of two pairs of strong hydrogen bonds, which create a one-dimensional polymeric structure with the interdimer Cu···Cu separation 4901(2) A It is believed that these hydrogen bonds between the copper(II) atoms are responsible for the unique magnetic properties of compound 1 The magnetic susceptibility of complex 1 exhibits a maximum at 6 K A satisfactory explanation was found with the Bleaney–Bowers equation for Cu–Cu interaction through carboxylato groups and H-bond bridges (2J = –683 cm–1) An additional molecular field correction that was used to characterize the interaction across the nia bridges is assumed to be extremely weak (zJ′ = –028 cm–1) (© Wiley-VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2006)

Copper (ii) coordination compounds: classification and analysis of crystallographic and structural data

Abstract: This review summarizes the data for over twelve hundred four - and five - coordinate copper(II) coordination compounds. The four-coordinate derivatives are mostly distorted square-planar. The five-coordinate derivatives are mostly square-pyramidal. The most common ligands are oxygen- and nitrogen- donors. There is a trend for the Cu-L distance to increase with covalent radius of the coordinated atom and also increasing coordination number. There are three types of isomerism - distortion, cis- and trans- and configuration. Several relationships are found and discussed.

Crystallographic and Structural Analysis of Iron Heterometallic Compounds Part II. Heterotrinuclear Compounds

Abstract: The chemistry of iron has an active area of research, particularly in the fields of catalysis and biochemistry. This review includes eighty-five double salts of iron and over eight hundred and fifty heterobinuclear iron compounds of known crystal structure. The heterometal atoms include non transition and transition metals, as well as lanthanides and actinides. Correlations between structural parameters, heterometal and ligand donor atoms are developed and an overall summary of the metal metal distances is given. CONTENTS 0. ABBREVIATIONS

Poly[[bis­(salicylato-κO)copper(II)]-di-μ-3-pyridylmethanol-κ2N:O;κ2O:N]: a redetermination at 100 K

Abstract: The crystal structure of the polymeric title compound, [Cu(C7H5O3)2(C6H7NO)2]n, has been reported previously at room temperature by Hoang, Valach, Macaskova & Melnik [Acta Cryst. (1992) C48, 1933–1936]. The centrosymmetric coordination environment of CuII at 100 K displays elongation of the Cu—N bonds and contraction of the Cu—O bonds to the 3-pyridylmethanol ligands, compared with the room-temperature structure. The Cu—O bond lengths to the carboxyl­ate groups of the salicylate ligands are comparable at both temperatures.