Synthesis, crystal structures and magnetic properties of transition metal-azide complexes coordinated with pyridyl nitronyl nitroxides

Two novel complexes Co(N-3)(2)(PNN)(4) (I) and Mn(N-3)(2)(PNN)(2)(CH3OH)(C2 H5OH) (II) (PNN = 2-(p-pyridyl)-4,4,5,5-tetramethylimidazoline-1 -oxyl-3-ox ide) were synthesized and characterized by infrared spectra, elemental anal yses and UV-Vis techniques. The crystal structures of both complexes have b een determined by X-ray diffraction analysis. Complex I is a neutral five-s pin system and adopts a centrosymmetric tetragonally compressed octahedral coordination geometry in which Co(ll) ion is coordinated to four radicals t hrough the nitrogen atoms of the pyridine rings and two azide anions occupy ing the axial positions. Complex II is a neutral three-spin system in which Mn(ll) ion is bound to two azide anions, two alcohol molecules and two rad icals through the nitrogen atom of pyridine rings, and shows one-dimensiona l chain structure via hydrogen bonds (d(O . . .N) = 2.78 A). The magnetic p roperties for complexes I and II have been investigated in the temperature range 2-300 K. A theoretical model has been developed for complex I and the magnetic behaviors for both complexes have been discussed in detail. (C) 2 001 Elsevier Science B.V. All rights reserved.