Dušan Valigura

Field Supported Slow Magnetic Relaxation in a Mononuclear Cu(II) Complex

A mononuclear hexacoordinate Cu(II) complex shows a field induced slow magnetic relaxation that is not facilitated by an energy barrier to spin reversal due to the zero-field splitting. Two relaxation channels were found: the magnetic field strongly supports the low-frequency relaxation path with a relaxation time as long as τ = 0.8 s at T = 1.9 K and B = 1.5 T. The mechanism of the relaxation at low temperature involves the dominant Raman process for this S = 1/2 spin system along with a temperature-independent term belonging to a quantum tunneling.

A bridge-bond isomerism. X-Ray crystal structure, spectral and magnetic properties of two dinuclear isomeric complexes [Cu(bipyo)Cl2](bipyo = 2,2′-bipyridine N,N′-dioxide)

Copper(II) chloride reacts with 2,2′-bipyridine N,N′-dioxide (bipyo), in methanolic solution, in a manner depending on the reaction conditions (temperature, ligand : metal ion ratio, concentration, etc.) to form different products. Two of them, a green and a yellow-orange isomer of [Cu2(bipyo)2Cl4], have been characterized by elemental microanalysis, electronic, IR and ESR spectra and magnetic susceptibility measurements. The crystal and molecular structures of both isomers have been determined from X-ray diffractometer data by the heavy-atom method and refined by full-matrix least-squares. The structures of the green and yellow-orange isomers, respectively, have been refined to R= 0.054 (for 1366 reflections) and 0.063 (for 1283 reflections): green isomer, triclinic, space group P, a= 8.664(2), b= 8.732(2), c= 9.099(3)A, α= 95.62(2), β= 107.04(2), γ= 114.05(2)°, and Z= 1; yellow-orange isomer, monoclinic, space group P21/c, a= 7.912(2), b= 9.878(2), c= 15.086(3)A, β= 99.86(2)° and Z= 2. Both crystal structures comprise centrosymmetric dimeric [Cu2(bipyo)2Cl4] molecules. The copper(II) atoms of the green isomer are bridged by two chlorine atoms, those of the orange-yellow isomer by the oxygen atoms of two bipyo ligands.

Synthesis, structure, spectral and magnetic properties of 4-methoxy- and 3-methylsalicylatocopper(II) complexes with 2-pyridylmethanol

The synthesis and characterization of [Cu(4-MeOsal)2(2-pyme)2] (1) and [Cu(3-Mesal)2(2-pyme)2] (2) (where 4-MeOsal = 4-methoxysalicylate, 3-Mesal = 3-methylsalicylate and 2-pyme = 2-pyridylmethanol) are reported. The composition and stereochemistry as well as the mode of coordination have been determined by elemental analysis, IR, electronic and EPR spectra as well as magnetization measurements over the temperature range 1.8–300 K. The crystal structures of Cu(4-MeOsal)2(2-pyme)2 and Cu(3-Mesal)2(2-pyme)2 have been determined.

1H‐Nicotinamidium 3,5‐di­nitro­salicyl­ate

Institut of Chemistry,University of Wroclaw, F. Joliot-Curie 14,50 383 Wroclaw, PolandCorrespondence e-mail: koman@chtf.stuba.skKey indicatorsSingle-crystal X-ray studyT = 293 KMean ˙(C–C) = 0.003 A˚Disorder in main residueR factor = 0.040wR factor = 0.110Data-to-parameter ratio = 9.6For details of how these key indicators wereautomatically derived from the article, seehttp://journals.iucr.org/e.# 2003 International Union of CrystallographyPrinted in Great Britain – all rights reserved

Synthesis, spectroscopic characterization, and magnetic properties of a mixed-valence copper(I,II) acetato complex with triphenylphosphine. Crystal structure of hexa-µ-acetato-tetrakis(triphenylphosphine)tetracopper(I,II)

Copper(II) acetate reacts with triphenylphosphine, in ethanol solution, in a manner depending on the concentration of Cu(O2CMe)2, the molar ratio of PPh3 to CuII, and temperature, to form the copper(I) complex [Cu(O2CMe)(PPh3)n](n= 2 or 3), the copper(II) complex [Cu2(O2CMe)4(PPh3)2], and the mixed-valence copper(I,II) complex [Cu4(O2CMe)6(PPh3)4]. The pale blue-green complex [Cu4(O2CMe)6(PPh3)4] has been characterized by microanalysis, electronic, i.r., and e.s.r. spectra, and magnetic susceptibility measurements. The crystal and molecular structure of [Cu4(O2CMe)6(PPh3)4] has been determined from X-ray diffractometer data by the heavy-atom method and refined by full-matrix least-squares methods to R= 0.0565 for 2 227 reflections. Crystals are triclinic, space group P, with a= 10.898(8), b= 12.850(4), c= 19.877(8)A, α= 121.03(2), β= 90.14(5), γ= 117.98(4)°, and Z= 1. The crystal structure comprises centrosymmetrical molecules of [Cu4(O2CMe)6(PPh3)4]. Each molecule consists of a Cu2(O2CMe)4 dimeric unit in the axial positions to which two molecular Cu(O2CMe)(PPh3)2 ligands are co-ordinated through the oxygen atom of each acetate group.

(3,5-Dinitro­benzoato-κO)bis­[(2-pyrid­yl)methanol-κ2N,O]copper(II) 3,5-dinitro­benzoate

Department of Inorganic Chemistry, SlovakUniversity of Technology, Radlinske´ho 9,SK-812 37 Bratislava, Slovak RepublicCorrespondence e-mail:jaroslava.maroszova@stuba.skKey indicatorsSingle-crystal X-ray studyT = 293 KMean (C–C) = 0.004 A˚Disorder in main residueR factor = 0.042wR factor = 0.111Data-to-parameter ratio = 15.1For details of how these key indicators wereautomatically derived from the article, seehttp://journals.iucr.org/e.

Methyl- and methoxysalicylatocopper complexes with 2-pyridylmethanol: Synthesis, spectral properties, structure and EPR characterization in solid-state and in solution

AbstractThe syntheses and characterizations of salicylatocopper(II) complexes of the formula Cu(X-sal)2(2-pyme)2 (X = 3-MeO (1), 4-MeO (2), 3-Me (3), 4-Me (4) and 5-Me (5), where 3-MeOsal− = 3-methoxysalicylate, 4-MeOsal− = 4-methoxysalicylate, 3-Mesal− = 3-methylsalicylate, 4-Mesal− = 4-methylsalicylate, 5-Mesal− = 5-methylsalicylate anion, and 2-pyme = 2-pyridylmethanol) are reported. The composition was determined by elemental analysis, and ligand coordination modes have been determined by spectroscopic methods (IR, UV-VIS). The crystal structure determination of [Cu(3-MeOsal)2(2-pyme)2] (1) and [Cu(5-Mesal)2(2-pyme)2] (5) have confirmed conclusions originally based on spectral data. EPR measurements of frozen water/methanol solutions containing different copper(II): 2-pyme molar ratios have indicated presence of complexes with only two nitrogen donor atoms bonded to each central atom.

Crystal and molecular structure of a new type of tetranuclear mixed valence copper complex: Cu4Ac6(Ph3P)4(Ac = O2CMe)

The crystal structure of Cu4Ac6(Ph3P)4 comprises centrosymmetrical molecules, each of which consists of a dimeric unit of Cu2Ac4, similar to that in the structure of copper(II) acetate monohydrate, with the copper(I) co-ordinated through the oxygen atom of the acetate group in both axial CuAc(Ph3P)2 units.

SOD mimetic activity of salicylatocopper complexes

Investigation of salicylatocopper complexes in the presence of a nitrogen donor ligand is a growing research area due to the interesting mimetic activities of such complexes. Here, three X-salicylatocopper (where X = 3-methyl, or 4-methoxy) complexes with three different N-donor ligands, [Cu(μ-menia)(3-Mesal)2(menia)(H2O)]2 (I), Cu(3-Mesal)2(denia)2(H2O)2 (II), Cu(4-MeOsal)2(2-pyme)2 (III), are presented (where 3-Mesal = 3-methysalicylate, 4-MeOsal = 4-methoxysalicylate, menia = N-methylnicotinamide, 2-pyme = 2-pyridylmethanol). The complexes were characterized by elemental analysis, IR and UV-VIS spectrophotometry. Cyclic voltammetry and the superoxide dismutase activity of the prepared complexes in solution were measured and the complexes were characterized by means of the inhibition concentration IC50. In addition, the superoxide dismutase (SOD) activity of these complexes was compared with those of the parent ligand copper acetate, native SOD enzyme, and the related copper complexes containing non-steroidal anti-inflammatory drugs. The resulting SOD activity was correlated to the composition, structure and redox stability of the prepared complexes. The best value of the inhibition concentration was found for complex I (IC50 = 2.24 µM), which classifies this complex into a group of good superoxide scavengers.

Methyl- and methoxysalicylatocopper complexes with 2-ethylbenzimidazole

Abstract Four new compounds of formulae [Cu(3-Mesal)2(etbzim)2] (1), [Cu(4-Mesal)2(etbzim)2] (2), [Cu(4-MeOsal)2(etbzim)2] (3), [Cu(5-MeOsal)2(etbzim)2] (4) where 3- or 4-Mesal = 3- or 4-methylsalicylate anionic ligand, 4- or 5-MeOsal = 4- or 5-methoxysalicylate anionic ligand, etbzim = 2-ethylbenzimidazole) have been prepared and characterised by elemental analysis and available spectral methods (EPR, UV-vis and IR spectra). EPR spectra of all measured complexes are axial symmetry. Other spectral methods led to conclusion that all prepared complexes probably contain the etbzim ligand coordinated in equatorial plane together with the asymmetrically bonded salicylato anions thus giving {CuN2O2O’O”} chromophore. The supposed structural motive for all prepared complexes might be simmilar to those benzoate complexes with benzimidazole [Cu(4-OHbz)2(bzim)2] and [Cu(4-Mebz)2(bzim)2] (4-OHbz = 4-hydroxybenzoate, 4-Mebz = = 4-methylbenzoate), but similarity with polymeric salicylate complex [Cu(sal)2(bzim)2]n cannot be excluded.