Juraj Kratsmar-Smogrovic

EPR, ligand field spectra and antimicrobial activity of some N-pyruvideneglycinatocopper(II) complexes

Abstract N-Pyruvideneglycinatocopper(II) complexes were synthesized of composition Cu(pyrgly)(L)(H 2 O) x with LH 2 O, x =2 ( I ); L=pyridine, x =2 ( II ); L=quinoline, x =2 ( III ); and L=aniline, x =1 ( IV ). The ligand field spectra provide evidence of a distorted octahedral Cu(II) coordination in ( I ) and ( III ), whereas in ( II ) and ( IV ) the coordination polyhedron around Cu(II) is square-pyramidal. According to the results of EPR spectra, the neutral ligand L strongly influences the weak exchange interactions between Cu(II) ions in the solid state. The effect of the ligand L on the local and cooperative symmetry is discussed. The complexes show antimicrobial activity, being most active against fungi.

EPR, ligand field spectra and antimicrobial activity of dimeric aryloxyacetatocopper(II) complexes with antipyrine

Abstract Copper(lI) complexes with aryloxyacetato ligands and antipyrine (Apy) of the general formula [Cu2- (RCOO)4(Apy)2] were prepared with RCOO− as phenoxyacetato, 3-methylphenoxyacetato, 4-methylphenoxyacetato, 4-chlorophenoxyacetato, 2-methyl- 4-chlorophenoxyacetato, 3-methyl-4-chlorophenoxyacetato and 2-naphthoxyacetato anions. The parameters of the triplet spin state EPR spectra at X and Q band frequencies (D|hc = 0.37 cm−1, g⊥ = 2.07, g‖ = 2.38, A‖|c = 0.007 cm−1) provide evidence of a dimeric carboxylato-bridged structure with apically bound antipyrine. The almost constant EPR data as well as the energies of the ligand field transitions at 77 K [dx2−y2 ← dxz, dyz (14000 cm−1), dx2−y2 ← dxy (11200 cm−1) and dx2−y2 ← dz2 (9500 cm−1)] indicate that the square-pyramidal geometry of the CuO5 polyhedra is nearly unaffected by the substituents on the aryloxyacetato group. The complexes show antimicrobial activity, being most efficient against Candida albicans and Bacillus subtilis.

Coordination geometries and cooperative ordering effects in copper(II) complexes with tridentate Schiff base dianions—III. EPR study on N-salicylideneglycinatocopper(II) complexes with thiourea derivatives

Abstract N-Salicylideneglycinatocopper(II) complexes of the composition Cu(salgly) (Ls)(H2O)x were synthesized with Ls = thiourea, N-methylthiourea, N,N,N′,N′-tetramethylthiourea, N-ethylthiourea, N,N′-diethylthiourea, N-(2-chlorophenyl)thiourea, N,N′-diphenylthiourea, N,N′-ethylenethiourea, N,N′-phenylenethiourea [≡ 1,3-dihydrobenzimidazole-2-thione]; and x = 0 or 1. The EPR spectra gave evidence for square-pyramidal coordination around CuII, however, with a different strength of axial interaction originating from an oxygen atom from the adjacent complex molecule. In the case of monohydrates bonding of a water molecule is also possible. In two examples, even square-planar geometry, without any significant axial interaction can be assumed. The great variety of cooperative ordering phenomena in the structure, which is caused mainly by the extraordinary flexibility of the Schiff base ligand, results in coupling patterns ranging from ferrodistortive to antiferrodistortive. These patterns are remarkably influenced by the substitutions on thiourea. Both the global and local symmetry effects are analysed with the aid of EPR spectroscopy.

EPR study of local and cooperative symmetry effects in N-salicylideneglycinatocopper(II) complexes

Abstract N-Salicylideneglycinatocopper(II) complexes of the composition Cu(salgly)(L)(H2O)x with L = imidazole, x = O (I); L = 2-propylimidazole, x = 1, (II); L = pyridine, x = O (III); L = pyrazole x = 1 (IV) and L = 3,5-dimethylpyrazole, x = 1 (V) were synthesized, The EPR and ligand field specra of these compounds as well as of N-salicylideneglycinatothioureacopper(II) (IV) give evidence for a square-pyramidal Cu(II) coordination. The EPR spectra of I, II, and III can be reasonably interpreted using axial molecular g tensors, whereas the molecular g tensors of IV, V and VI exhibit orthorthombic symmetry. The experimental EPR spectrum of VI shows molecular g values in accordance with the ferrodistortive order found previously by X-ray structure analysis. In V no exchange interactions between crystallographically nonequivalent Cu(II) ions were found. The complexes I–IV show exchange coupled g parameters, corresponding to an antiferrodistortive (I, III) or disturbed antiferrodistortive ordering (II, IV). The alkyl-substitution on the neutral ligand and the presence of water in the crystal structure strongly influence the exchange interactions between Cu(II) ions.

Coordination geometries and cooperative ordering effects in copper(II) complexes with tridentate Schiff base dianosis IV1. EPR monocrystal investigation of dipotassium-bis[(μ-isocyanato-N,O)-{N-salicylidene-(R,S)-α-alaninato}]dicuprate(II)

Abstract Some aspects of the crystal structure of dipotassium-bis[(μ-isocyanato-N,O)-{N-salicylidene-(R,S)-α-alaninato}](dicuprate(II), K2[Cu2{sal-R,S-ala}2(μ-NCO)2], necessary for the interpretation of EPR monocrystal spectra are reported The crystal structure consists of centrosymmetric binuclear [Cu2{sal-R,S-ala}2(μ-NCO)2]2− complex anions connected with the K+ ions by electrostatic forces. The coordination around CuII is approximately square-pyramidal. The basis of the pyramid is formed by the donor atoms O,N,O of the tridentate Schiff base ligand and the N atom of the addition NCO−. ligand. Completion of the pyramid is achieved by a weak apical contact ( CuO ′ = 2.70 A ) to the terminal O atom of the NCO− ligand within the dimeric unit. The two dimeric anions in the unit cell are mutually canted by an angle 2γ = 75.5°. The EPR powder spectrum shows molecular g components gx = 2.043, gy = 2.055, gz = 2.232. In measurements on the monocrystal two angular-dependent EPR lines, which are phase-shifted in the ab plane by the above canting angle 2γ, confirm the disturbed antiferrodistortive arrangement of two separate chains (nearest Cu⋯Cu spacing: 8.66 A) of ferrodistortively stacked CuII species.