A one-dimensional helical copper(II) imino nitroxide

The reaction of [Cu-I(CH3CN)(4)](PF6) with a biradical of imino nitroxide in methanol yielded a copper(II) complex [Cu-II(imapy)](PF6) (2) (Himapy = 2-(1'-oxy-4',4',5',5'-tetramethyl-4',5'-dihydro-1'H-imidazol-2'-yl)-6-(1 ''-oxyl-4 '',4 '',5 '',5 ''-tetramethyl-4 '',5 ''-dihydro-1 '' H-imidazol-2 ''-yl)pyridine)). In 2 one of the nitroxides in the ligand was reduced to a hydroxyamino anion and the Cu-I ion was oxidized. Complex 2 crystallizes in tetragonal space group P4(3)2(1)2 with a = 14.341(3) Angstrom, c = 24.282(5) Angstrom, V = 4993(1) Angstrom(3), and Z = 8, and the absolute structure for this crystal was determined by using Flack's parameter. Square planar coordination sites of the Cu-II ion are occupied by two nitrogen and two oxygen atoms, where one of the coordinated oxygen atoms comes from the hydroxyamino group in the next molecule. The Cu-II ions are bridged by the imino-hydroxyamino anion to form a one-dimensional structure with each Cu-II ion having the coordinated imino nitroxide. Complex molecules locate on the 4-fold screw axis, which results in a counterclockwise helical arrangement of the imino nitroxides. Magnetic susceptibility measurements revealed that antiferromagnetic interactions are operative. The system was treated as the one-dimensional chain of the Cu-II-radical species, and coupling constants J(1) and J(2) for the intrachain and Cu-II-radical interactions were estimated to be -6 and -23 cm(-1), respectively.