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  • Author: Jozef Miklovič x
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Abstract

The synthesis and characterization of nine new copper(II) complexes [Cu(2-Clnic)2L2] (where 2-Clnic is 2-chloronicotinate anion, L is imidazole – Im, benzimidazole – Bim, furo[3,2-c]pyridine – FP, 2-methylfuro[3,2-c]pyridine – MFP, or [1]benzofuro[3,2-c]pyridine – BFP), [Cu(2-Clnic)2(INA)] (where INA is isonicotinamide), [Cu(2-Clnic)2(4-py)]·H2O (where 4-py is 4-methylpyridine) and [Cu2(2-Clnic)4(IQ)2] (where IQ is isoquinoline) are reported. The characterizations were based on elemental analysis, infrared, electronic and EPR spectra. The dimeric character of [Cu2(2-Clnic)4(IQ)2] is assumed on the EPR spectrum and the other spectral methods. The crystal structure of the [Cu(2-Clnic)2(Bim)2] and [Cu(2-Clnic)2(FP)2] complexes have been determined by X-ray crystal structure analysis. Both complexes exhibit the hexacoordination coordination polyhedra around copper atom that lies in the crystallographic center of symmetry. The distorted tetragonal-bipyramidal (4+2) arrangement is in good agreement with spectral data that have suggested an asymmetric chelate coordination of the carboxylic group.

Abstract

The synthesis and characterization of eleven new Cu(II) and Co(II) complexes is reported. The complexes were characterized by elemental analyses, infrared and electronic spectra. Copper(II) with 3- methylthiophene-2-carboxylic acid (HMTK) forms a dinuclear complex of the acetate type [Cu2(MTK)4(H2O)2]. By reaction of this complex with 2-metylfuro[3,2-c]pyridine (MeFP), not only acetate type complexes [Cu2(MTK)4L2] (L= FP, MeFP) were obtained, but also monomeric complex [Cu(MTK)2(FP)2]. In the cases of [1]benzofuro[3,2-c]pyridine (BFP) and 2-(3-trifluoromethylphenyl) furo[3,2-c]pyridine (CF3FP) only monomeric complexes [Cu(MTK)2L2] (L = BFP, CF3FP) were obtained. It is possible to observe, that with increasing amount of the ligand, the yield of monomeric complexes increases too. In monomeric complexes, the carboxylic group of anionic MTK binds to atom Cu(II) by asymmetrically chelating O,O-coordination. The crystal structure of the complex [Cu(MTK)2(MeFP)2] was determined by X-ray single crystal structure analysis. The copper(II) atom lies in the crystallographic centre of symmetry in an distorted tetragonal-bipyramidal arrangement. The structure of this complex confirms an asymmetric chelate coordination of the carboxylic group. HMTK and Cobalt(II) form coordination compound [Co(H2O)6](MTK)2 with assumed ionic mode of coordination of anionic MTK. With furopyridines monomeric complexes [Co(MTK)2L2] (L= FP, MeFP, BFP, CF3FP) with distorted octahedral coordination polyhedron around Co(II), were formed.

Abstract

Thieno[3,2-c]pyridine (thpy) has been prepared in a free form and embodied into the [Ni(thpy)2(H2O)2(ac)2] complex as a ligand. The X-ray structure shows a molecular structure of the complex with Ni−O(ac) = 2.059, Ni−OH2 = 2.078, and Ni−N(thpy) = 2.124 Ǻ. Electronically the complex behaves like a compressed tetragonal bipyramid. The molecular units are linked into a complex system of hydrogen bonds. Two units show a π−π stacking of the aromatic rings (3.8 Ǻ). There are planes of tetragons formed of the nickel atom with the in-plane Ni...Ni separation of 7.74 Ǻ and the inter-plane Ni...Ni contacts at a = 9.65 Ǻ. The effective magnetic moment shows a gradual decrease on cooling from the room temperature and an abrupt drop below 20 K typical for the zero-field splitting of S = 1 systems. Above the room temperature the effective magnetic moment shows anomalies – a decrease and then an increase.