Ruthenium( II ) coordination to a model for the topasemiquinone cofactor of amine oxidases. Resolution of 1 H and 99,101 Ru EPR hyperfine structure

The paramagnetic complex (L2–˙) RuII(bpy)2, where L2–˙= 5-methyl-2-oxido-1,4-benzosemiquinone and bpy = 2,2′-bipyridine, was studied because the quinonoid form LH is a model of the topa-quinone (TPQ) cofactor of certain copper-dependent amine oxidases. For the metal complex the potential ortho- and para-quinonoid character of the LHn system was probed by high resolution EPR spectroscopy of the semiquinone state which could be obtained through oxidation of the basic catecholate form.