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

Abstract

The paramagnetic complex (L^2–˙) Ru^II(bpy)₂, where L^2–˙= 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 LH_n system was probed by high resolution EPR spectroscopy of the semiquinone state which could be obtained through oxidation of the basic catecholate form.