New ruthenium complexes, trans-[RuX2(L)] (L=tetradentate 6,6'-bis(oxazolinyl or benzimidazolyl)-2,2'-bipyridine; X=halide or cyanide ion) have been synthesized. The present Ru complexes reveal a stable Ru(II/III) oxidation process and exhibit strong MLCT bands around 450-600 nm. The oxidation potential depends on the axial halogeno ligand; the potential increases in the order of X=Cl