Diastereoisomeric dinuclear ruthenium complexes of 2,5-di(2-pyridyl)thiazolo[5,4-d]thiazole

The first metal complexes of 2,5-di(2-pyridyl)thiazolo[5,4-d]thiazole (5) are described. X-Ray crystal structures are reported for the free ligand 5, a dinuclear copper complex 6 and the two diastereoisomers, 7meso and 7rac, of the dinuclear bis(2,2'-bipyridine)ruthenium complex. The two diastereoisomers of 7 and the 4,4'-dimethyl-2,2'-bipyridine analogue 8 are readily separated by cation exchange chromatography. 1H NMR and visible absorption spectra and electrochemical data for the four dinuclear ruthenium complexes reveal that these have relatively small HOMO-LUMO energy gaps and exhibit relatively weak metal-metal interactions.