STRONG ANTIFERROMAGNETIC EXCHANGE INTERACTIONS IN COBALT(II) COMPLEXES WITH 2-PYRIDYL SUBSTITUTED NITRONYL NITROXIDE LIGAND

Three new complexes, [Co(hfac)(2)(NIToPy)] (1), [CoCl2(NIToPy)(2)] (2) , and [Co(NIToPy)(3)](ClO4)(2) (3), with NIToPy = tetramethyl-4,5-dihy dro-1H-imidazolyl-oxy-3-oxide, and hfac = hexafluoroacetylacetonate, h ave been synthesized. The compound 3 crystallized in the monoclinic sp ace group P2(1), with two molecules in a unit cell of dimensions a = 1 0.565(4) Angstrom, b=14.714(9) Angstrom, c=14.596(7) Angstrom, and bet a = 107.10(4)degrees. The temperature-dependent magnetic susceptibilit y measurements (4.2 K-300 K) for the complexes demonstrated strong ant iferromagnetic exchange interaction between cobalt(II) ion and NIToPy radical spins with J = -140.1 cm(-1) for 1, J = -94.2 cm(-1) for 2, an d J = -161.8 cm(-1) for 3, respectively. The magneto-structural correl ation in these complexes has been discussed.