Magnetic interactions in spin-labelled glycine complexee to cupric ions

Summary The interactions between cupric ions and a paramagnetic aminoacid ligand labelled with a nitroxide group were investigated by visible and e.p.r. spectroscopies. Glycine substituted on the carboxylic acid function with 4-amino-2,2,6,6-tetramethylpiperidineN-oxide forms complexes with cupric ions which show strong magnetic interactions between the paramagnetic centers. At high pH values, averaged g and hyperfine coupling parameters are observed with g=2.05 and a=30 gauss, corresponding to a complex formed with two ligands coordinated to the cupric ions. The presence of other species is discussed.