In recent years, the interaction between small molecular transition metal complexes and DNA has been an active subject at international bioinorganic chemistry field. Octahedral polypyridyl transition metal complexes have been used extensively as DNA structural probes, molecular light-switch, electron transfer for DNA, DNA footprinting reagents and DNA cleavaging reagents and so on. Compare with other metal complexes, polypyridyl ruthenium complexes have A- and A- isomers, and they all have special photophys...