Jozef Švorec

A study of copper(II) carboxylato complexes with the biological ligands nicotinamide and papaverine

The X-band Electron Spin Resonance spectra, ESR, of Cu(II) complexes with the carboxylic acids, HCOOH, CH3COOH, ClCH2COOH, Cl2CHCOOH, Cl3CCOOH, F2ClCOOH, CH3CH2COOH, niflumic acid and the ligands nicotinamide and papaverine have been studied. The compounds form either mononuclear or binuclear structures which can be qualitatively correlated with the strengths of the acid and base. Analysis of the spin Hamiltonian parameters for the monomeric species indicate that the molecule has nearly axial symmetry ðgk . g’Þ with the unpaired electron in the dx2 –y 2 orbital. In many cases the perpendicular feature is sufficiently well resolved showing superhyperfine features due to the nitrogen ligand nuclei. Ak varies over the range 130 ! 188 G and the variation appears to arise as a consequence of changes in gk: The dimeric species show ESR spectra typical of Cu(II)-carboxylate complexes which consist of 3 (4 if E – 0) lines. These are assigned to Bz1; Bx2;y2 and Bz2 since the Q-band spectra of similar molecules indicate that the Bx1;y1 transition(s) lies below Bz2 which is itself near zero field. The observed seven-line hyperfine coupling on the Bz1 transition of some of the dimeric complexes is due to the two equivalent copper nuclei ðI ¼ I1 þ I2 ¼ 3Þ: The singlet – triplet separation has been estimated from the spin Hamiltonian parameters to give values of l2Jl in the range of approximately 220– 290 cm 21 which are typical of the compounds of this type.

Crystal structures and spectroscopic behaviour of polymeric copper(II) chloroacetate adducts with 3- and 4-pyridylmethanol

The structural and spectroscopic properties for polymeric complexes, Cu(Cl2CHCOO)2(3-PM)2, Cu(Cl3CCOO)2(3-PM)2, Cu(ClCH2COO)2(4-PM)2 and Cu(Cl2CHCOO)2(4-PM)2 (PM ¼ pyridylmethanol), are reported. The characterization is based on elemental analysis, infrared, electronic and EPR spectra. The Cu(Cl2CHCOO)2(3-PM)2 as well as Cu(Cl3CCOO)2(3-PM)2 adopt polymeric structures as revealed by X-ray structure analysis. The polymeric structure of Cu(Cl2CHCOO)2(3-PM)2 is centrosymmetric and centred at the inversion center of the space group P1bar (Z ¼ 2), while the structure of Cu(Cl3CCOO)2(3-PM)2 contains two crystallographically independent centrosymmetrical molecules, which are centred at the inversion centres of the space group P21/c (Z ¼ 4). 2003 Elsevier B.V. All rights reserved.

Synthesis, spectral properties, crystal structures and biological activity of copper(II) pyridinecarboxylates with N -heterocyclic ligands

Synthesis and characterization of four new 2,6-dimethoxynicotinate (2,6-(MeO)2nic) copper(II) monomeric complexes [Cu(2,6-(MeO)2nic)2(py)2] (py is pyridine), [Cu{2,6-(MeO)2nic}2(Etnic)2(H2O)] (Etnic is ethylnicotinate), [Cu{2,6-(MeO)2nic}2(Et2nia)2(H2O)2] (Et2nia is N,N-diethylnicotinamide) as well as of the polymeric complex [Cu{2,6-(MeO)2nic}2(ron)2] n (ron is ronicol) are reported. The characterizations were based on elemental analysis, infrared, electronic and EPR spectra. Crystal structures of two of the complexes have been determined. The copper(II) of [Cu{2,6-(MeO)2nic}2(py)2] has a distorted tetragonal-bipyramidal (4 + 2) coordination environment. Both 2,6-(MeO)2nic anions are asymmetrically chelating. The Cu(II) of [Cu{2,6-(MeO)2nic}2(Etnic)2(H2O)] is pentacoordinate in a slightly distorted tetragonal-pyramidal arrangement by two trans nitrogens, each of one Etnic, by two oxygens, each of the carboxyl group of one unidentate 2,6-(MeO)2nic and the axial position occupied by water at a longer distance. Antimicrobial effects of the complexes have been tested on various strains of bacteria, yeasts and filamentous fungi. While the 2,6-(MeO)2nicH alone did not influence the model bacteria growth, dimeric [Cu{2,6-(MeO)2nic}2(H2O)]2 and polymeric [Cu{2,6-(MeO)2nic}2(ron)2] n have pronounced influence on the growth of Staphylococcus aureus, Escherichia coli and Candida parapsilosis.

Different structural types of copper(II) furan- and thiophencarboxylates: X-ray structural, EPR, spectral and magnetic analyses

Synthesis and characterization of eight new complexes of various structural types are reported. With 5-nitro-2-furancarboxylic acid (5-NO2-2-fucH), two monomeric complexes, [Cu(5-NO2-2-fuc)2(H2O)2] (II) and [Cu(5-NO2-2-fuc)2(H2O)4] (III), as well as a dimeric complex with ethylnicotinate (Etnic), [Cu(5-NO2-2-fuc)2(Etnic)2]2 (V), were prepared. With other acids: 2,5-dimethyl-3-furancarboxylic acid (2,5-Me2-3-fucH), 2-thiophencarboxylic acid (2-tpcH), 3-methyl-2-thiophencarboxylic acid (3-Me-2-tpcH) or 5-methyl-2-thiophencarboxylic acid (5-Me-2-tpcH), only dimeric complexes [Cu(2,5-Me2-3-fuc)2(H2O)]2 (I), [Cu(2,5-Me2-3-fuc)2(Etnic)]2 (IV), [Cu(2-tpc)2(Etnic)]2 (VI), [Cu(3-Me-2-tpc)2(Etnic)]2 (VII) and Cu(5-Me-2-tpc)2(Etnic)]2 (VIII) have been synthesised. Characterizations of the complexes were based on elemental analysis and infrared, electronic, EPR and magnetic measurements. Moreover, complexes III, V, VII and VIII were also studied by X-ray structural analysis. Two structural types of dimeric complexes were observed differing in the number of carboxylate bridges. Most of the dinuclear complexes exhibit the common “paddle-wheel” structural motif while the molecular structure of V contains two pentacoordinated copper(II) ions bridged by two carboxylate groups of two 5-nitro-2-furancarboxylate ligands resulting in the intramolecular copper-copper distance of 4.4960(8) Å. Magnetic properties (monomeric EPR signal and isotropic exhchange constant (J of approximately 0 cm−1) of V confirmed a very weak magnetic interaction between copper centres.

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.

Structural study and magnetic properties of copper(II) thiophene-2-carboxylate with 4-pyridinemethanol and isonicotinamide

The synthesis and characterization of [Cu(5-Me-2-tpc)2(4-pyme)2] (I), [Cu(3-Me-2-tpc)2(4-pyme)2] (II), [Cu(2-tpc)2(4-pyme)2] (III), [Cu(2-tpc)2(isonia)2(2-tpcH)] (IV), [Cu(5-Me-2-tpc)2(isonia)2(5-Me-2-tpcH)] (V), [Cu2(2-tpc)4(4-pyme)2] (VI), [Cu2(3-Me-2-tpc)4(isonia)2] (VII) (where 2-tpc is 2-thiophenecarboxylate, 3-Me-2-tpc is 3-methyl-2-thiophenecarboxylate, 5-Me-2-tpc is 5-methyl-2-thiophenecarboxylate and 4-pyme is 4-pyridinemethanol and isonia is isonicotinamide) are reported. The complexes under study were characterized by electronic, IR and EPR spectroscopy, magnetic susceptibility over the temperature range and X-ray structure analysis. Structural studies revealed a distorted tetragonal-bipyramidal environment around the copper ion for monomeric complexes I–V. The structure of dimeric complexes VI and VII consists of units of the known paddle-wheel dicopper(II) tetracarboxylates, which are made up of four thiophene-2-carboxylate ions thus bridging the two copper atoms. The complex molecules of all compounds are connected through H-bonds into supramolecular chains or frameworks. The spectral and magnetic properties are discussed with regard to X-ray data.

Effects of [Cu(2-MeSNic)2(MeNia)2(H2O)2]·H2O and [Cu(2-MeSNic)2(H2O)]2 on Candida albicans

Abstract Probable mode of action of new copper complexes of 2-methylthionicotinate (2-MeSNic) of composition [Cu(2-MeSNic)2(H2O)2] and [Cu(2-MeSNic)2(MeNia)2(H2O)2]·H2O (where MeNia is N-methylnicotinamide) is described. Both partial growth inhibition of Candida albicans (IC50 ≥ 1.78 mmol·L−1, MIC ≥ 2.5 mmol·L−1) and leak of proteins into the extracellular space (more than 80 %) were observed in the presence of these copper complexes. The membrane damage was detected by staining with Hoechst 33342, propidium iodide and methylene blue. Ascorbic acid potentiated antifungal activity of copper complexes approximately seven-fold and induced the oxidative stress, respectively. The production of intracellular reactive oxygen species was visualized by dichlorofluorescein. Thiobarbituric acid-reactive substances were formed as a by-product of lipid peroxidation.

Some aspects of dimeric metylsalicylatocopper(II) complexes preparation

Abstract A systematic study of the preparation of methylsalicylatocopper(II) complexes with or without N-donor ligand has resulted in three new dimeric complexes formation. The investigation has been targeted to two main aspects: the conditions of dimeric complexes preparation and the properties of obtained products. The common stoichiometric formula for all three complexes is Cu(x-MeSal)2(H2O)(ACN)z (where x-MeSal = 3- or 4-methylsalicylate anion, ACN = acetonitrile and z = 0, 1). Used spectral measurements mainly EPR spectroscopy gave the proof about the existence of dimeric “paddle-wheel” units in all three complexes. Moreover, it was concluded that acetonitrile molecules are more probably bonded to copper(II) atoms in apical positions of dimeric units. The water molecules are in coordination sphere only in the case when acetonitrile is not present. However data show that presence of 4-methylsalicylate anions led to strengthening of Cu-N bonds.