Stereochemical control of donor and acceptor groups in a monomeric chromophore-quencher complex of ruthenium(II)

The chromophore−quencher complex [Ru(Me₂bpy)(bpy-MV²⁺)(bpy-PTZ)]⁴⁺, containing one donor (phenothiazine, PTZ) and one acceptor (methyl viologen, MV²⁺) functionality, has been synthesized and separated into its four geometric isomers. This was achieved through the intermediacy of [Ru(Me₂bpy)(bpy-MV²⁺)(py)₂]⁴⁺, the two isomers of which were separated and each reacted stereoselectively with bpy-PTZ to produce two distinct isomer pairs of the target molecule. Cation-exchange chromatography allowed separation to realize the four forms. The isomers of the product and of the intermediates were characterized by NMR spectroscopy. This is the first example of the isolation of geometric isomers of a mononuclear system containing a single donor and single acceptor functionality