Unusual magnetic properties of the adduct of copper chloride with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide

A stable adduct was isolated from copper(I1) chloride and the stable free radical 2-phenyl-4,4,5,5-tetramethylimidazoline- 1-oxy1 3-oxide. The stoichiometry of the adduct is 1:2, and a crystal structure analysis has shown the copper ion to be four planar coordinated by two chlorine atoms and two oxygen (nitroxyl) atoms. The nitroxyl ligands are bound with a short Cu-0 distance of 1.988 (1) A. Magnetic measurements show that this material is in a doublet state from 30 to 300 K. At lower temperature a spin airing process became operative. Crystal data: monoclinic, P2,/n, a = 11.988 (4) A, b = 10.878 (3) A, c = 11.788 (4) H , @ = 106.14 ( 2 ) O , 2 = 2.