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Two types of bromido and chlorido complexes with 3-hydroxypyridine (3-pyOH), namely, [CuX2(3-pyOH)4] (1, 2) type A, and [Cu(μ-X)2(3-pyOH)2]n (3, 4) type B (X = Br, Cl) were prepared. The X-ray single crystal structure determination of the mononuclear [CuBr2(3-pyOH)4] 1 reveals octahedral coordination with four nitrogen atoms of 3-pyOH molecules in the equatorial plane and two bromido anions in the axial positions. A structure of the type A chlorido analogue [CuCl2(3-pyOH)4] 2 was determined by a combination of the powder and the single crystal diffraction data. The molecular structure of the type B bromido complex [Cu(μ-Br)2(3-pyOH)2]n 3 was also determined from the single crystal XRD data. Herein, infinite linear chains of catena-di-μ-bromidobis(3-pyOH)copper(II) are present. A comparison of the powder diffraction data of compounds [Cu(μ-X)2(3-pyOH)2]n 3 and 4, together with their results of IR, UV-Vis and magnetic methods show, that both compounds 3 and 4 can be assigned as the type B, due to their probably very similar molecular structure. The magnetic susceptibility of the type A mononuclear complexes shows a paramagnetic behaviour in the range 2-300 K with a constant χM · T value. On the other hand, a broad maximum of the curve χM versus T below 50 K for the type B polynuclear complexes, reveals the antiferromagnetic interaction between the copper(II) S = ½ magnetic moments. These data were fitted by the Bonner-Fisher curve (1D Heisenberg antiferromagnet) giving J -17 cm-1 (3), -10 cm-1 (4). The paramagnetic behaviour of the polynuclear complexes 3, 4, noticed from the room temperature EPR spectra, is in agreement with the spin of copper(II), and the rhombic distortion of the spin tensor close to the axial symmetry. [ABSTRACT FROM AUTHOR]

The chemistry of copper(H) is widely described in the literature due to its importance in various fields of research and because of the relative ease in the synthesis of new compounds. The magnetochemistry is one of these fields. However the results obtained with 'the magnetic methods' e. g. EPR and magnetic susceptibility, that may enable important insight in the properties of the compounds, are very often ambiguous. The structural correlation of the wide range of copper(II) complexes with the magnetic analysis can fulfil some gaps in this area. A series of copper(II) complexes, synthesized in our lab during the last decade, is discussed. [ABSTRACT FROM AUTHOR]

The title compounds, tetrakis(μ-benzoato- O: O′)­bis(2,6-di­amino­pyridine)-1κ N,2κ N-dicopper(II)-aceto­nitrile (1/2), [Cu2(C7H5O2)4(C5H7N3)2]·2C2H3N, (I), and bis­(aceto­nitrile)-1κ N,2κ N-tetrakis(μ-benzoato- O: O′)­dicopper(II)-aceto­nitrile (1/1.5), [Cu2(C7H5O2)4(C2H3N)2]·1.5C2H3N, (II), crystallize as aceto­nitrile solvates exhibiting different stability. They have similar molecular structures with discrete dimeric units located at crystallographic inversion centres. The copper ions are bridged by four benzoate groups and neutral N-donor ligands, viz. 2,6-di­amino­pyridine in (I) and aceto­nitrile in (II), are coordinated at apical positions. The diverse stability is probably due to hydrogen-bond interactions of the solvated aceto­nitrile mol­ecules with neighbouring dimers in compound (I). [ABSTRACT FROM AUTHOR]

In the title compound, [Cu2(CHO2)2(C5H4NO)2(C5H5NO)2]·1.02CH3CN, the dimeric unit is centrosymmetric, with two bidentate pyridin-2-olate and two bidentate formate syn– syn bridges, and two apical 2-pyridone ligands coordinated through the O atoms. The N atom from the apical 2-pyridone ligand is a donor of a hydrogen bond to the O atom of the bridging pyridinolate ligand of the same complex. The coordination polyhedron of the Cu atom is a distorted square pyramid. [ABSTRACT FROM AUTHOR]

A new ionic compound (C5H6NO)2 [Cu2(μ-O2CH)4(O2CH)2], 1 formed of 4-hydroxypyridinium cations and a complex anion was synthesized. The anion is a paddle-wheel dicopper carboxylate complex with four syn,syn-bridging and two axial anionic methanoato ligands. The XRD structure determination of 1 reveals that the molecular structure is stabilized by two H-bonds between the cations and the axial paddle-wheel anions (N-H…O 2.755(3), O-H…O 2.489(2) Å). The compound exhibits a very strong (2J = 500 cm-1) intra-binuclear antiferromagnetic interaction noticed already at room temperature attributed to the methanoato intra-binuclear bridges. The typical EPR S = 1 spin system signals of the dicopper paddle-wheel complexes at 90 and 450-700 mT are found in the room temperature spectrum, but they are poorly seen in the 110 K spectrum. These signals are of very low intensity and are accompanied by a dominant signal at 320 mT, all closely related to a very strong antiferromagnetic interaction present in 1. [ABSTRACT FROM AUTHOR]