Synthesis,Crystal Structure and Magnetic Properties of a Cobalt(Ⅱ) Complex with Quinoxaline-substituted Nitronyl Nitroxide Radicals

A new complex with the formula [Co(acac)_2(NITQ)_2]×2CH_2Cl_2 1(acac = acetylacetone, NITQ = 2-(2′-quinoxalinyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), was synthesized and elucidated structurally as well as magnetically in detail. The crystal belongs to the monoclinic system, space group P2_1/c with a = 9.6896(1), b = 20.539(4), c = 12.147(2) ?, β = 93.84(3)°, M_r = 997.65, V = 2412.1(8) ?~3, Z = 2, Dc = 1.374 g/cm, F(000) = 1038, m = 0.635 mm~(-1), the final R = 0.0539 and w R = 0.1289 for 5998 observed reflections(I 2σ(I)). The Co(Ⅱ) ion is coordinated by two nitrogen atoms of quinoxaline rings from two NITQs and four oxygen atoms from two acac ions to complete a distorted octahedral coordination environment. Compound 1 is further linked into a three-dimensional(3D) supramolecular network by hydrogen-bonding, Cl×××O weak contact and π···π stacking interactions. The magnetic measurements show compound 1 exhibits weak ferromagnetic interactions.