Linear-chain gadolinium(III) nitronyl nitroxide complexes with dominant next-nearest-neighbor magnetic interactions

Gd (hfac), NITiPr (hfac = hexafluoroacetylacetonate;N ITiPr = 2-isopropyl-4, 4, 5, 5-tetramethyl-4, 5-dihy1rH o--i midazolyl-l- oxy13-oxide) crystallizes in the monoclinic space group P 2, / n with cell parameters a = 11. 916 (1) A, b = 17. 625 (9) A, c = 18. 055 (I) A, j3 = 96. 98 (I) ’, V = 3763. 82 A’, and Z = 4. The structure refinement converged to R = 0. 086. The molecular structure the complex consists of linear chains made up by gadolinium (II1) ions bridged by nitronyl nitroxide radicals. The magnetic of this compound and of other structurally strictly related lanthanide nitronyl nitroxide complexes are discussed according a model in which the next-nearest-neighbor interactions are explicitly taken into account. For appropriate values of the exchange the ground state corresponds to a two-spins-up, two-spins-down configuration, which justifies the low effective magnetic observed at low temperature