Halogenido Analogues of Structuraly Diverse Complexes With 3-Hydroxypyridine

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 [Cu- Cl2(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 XM • T value. On the other hand, a broad maximum of the curve XM 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.