Alizarin, 1,2-dihydroxy-9-10-anthraquinone, can bind the bis(bipyridine)ruthenium(II) moiety, [Ru(bpy)2]2+, at both the (1,2) catechol-like fragment and the (1,9) acetylacetonate-like fragment. These linkage isomers may be freely interconverted by thermal and protonation processes.