Structure and magnetic properties of linear-chain complexes of rare-earth ions (gadolinium, europium) with nitronyl nitroxides

Gd(hfac),NITEt (hfac = hexafluoroacetylacetonate, NITEt = 2-ethyl-4,4,5,5-tetramethyl-4,5-dihydro-lH-imidazolyl-l-oxyl 3-oxide) crystallizes in the monoclinic space group P21/n with cell parameters a = 2006.4 (4) pm, b = 1706.4 (4) pm, c = 2267.3 (2) pm, fi = 113.82 (1)O, V = 7101.3 X lo6 pm3, Z = 4, and R, = 0.076. The crystal structure consists of linear chains made by Gd(hfac), moieties linked by bridging nitroxide radicals. The magnetic behavior shows the presence of an antiferromagnetic coupling. Several models for interpreting the magnetic structure are proposed and discussed.