Several new TEMPO (2, 2, 6, 6-tetramethylpiperidine N-oxide)-1abeled ruthenium complexes were prepared. They can be discerned in two different classes featuring rigid and flexible linkers between the ruthenium (II)-polypyridyl complex and the stable nitroxide. The bis (heteroleptic) ruthenium complexes were synthesized from [Ru (L2)] C12 (L= 2, 2'- bipyridine or 1, 10-phenanthroline) and newly prepared phenanthroline-TEMPO-ligands. ...