MOLECULAR MAGNETS BASED ON NICKEL(II) COMPLEXES WITH 3-IMIDAZOLINE NITROXIDES AND ALCOHOLS

Crystallization of heterospin bischelate NiL2, where L is deprotonated nitroxide ylidene)-2,2,5,5-tetramethyl-3-imidazoline-1-oxyl, with alc ohols allows a logical assembly of layered [NiL2(CH3OH)(2) (1) and NiL 2(C2H5OH)(2) (2)] or frame compounds [NiL2(HO(CH2)(4)OH) (3) and NiL2( HO(CH2)(5)OH) (4)]. The structures of complexes 1, 2, and 4 have been determined. Crystal data: 1, monoclinic, space group P2(1)/c, a = 8.92 9(2) Angstrom, b = 15.773(3), c = 11.518(2), beta = 118.84(1)degrees, Z = 2; 2, monoclinic, space group P2(1)/c, a = 9.923(5) Angstrom, b = 15.992(5) Angstrom, c = 11.486(2) Angstrom, beta = 120.63(3)degrees, Z = 2; 4, monoclinic, space group C2/c, a = 21.028(4) Angstrom, b = 10. 943(2), c = 14.405(3), beta = 110.61(3)degrees, Z = 4. The structure o f 3 is very close to the structure of 4 and has been reported earlier. Robust H-bonding between the OH groups of the coordinated alcohols an d the >N-O-. groups of the neighboring fragments NiL2 leads to the for mation of polymeric layers in the solid. At the same time, hydrogen bo nds form effective channels for magnetic interactions >N-O-. ... H-O-R -Ni2+-O-R-H ... O-.-N<. The magnetic phase transition to the weak ferr omagnetic state below 7 K is inherent in 1-4. For 2 and 4, this transi tion is induced by the external magnetic field that correlates with th e elongation of Ni-O-R and O-R ... O-.- distances in the exchange chan nels >N-O-. ... H-O-R-Ni2+-O-R-H ... O-.-N< in solids 2 and 4 compared to 1 and 3. It has been found that magnetic ordering occurs only with in the polymeric layers formed due to multiple hydrogen bonds. Investi gation of the anisotropy of magnetic susceptibility performed on large single crystals of 1-4 revealed an essentially different ordering of the magnetic moments of magnetic sublattices in 1, 2 and in 3, 4.