Neutral ruthenium(II) complexes [RuLL'(CN)(2)] (L, L' = bpy, dmb, dbb; bpy = 2,2'-bipyridine, dmb = 4,4'-dimethyl-2,2'-bipyridine, dbb = 4,4'-tert-butyl-2,2'-bipyridine) were prepared, and the luminescence characteristics of the complexes in the solid state were measured. The luminescence was tuned by crystal waters included in the crystals; for example, [Ru(dbb)(2)(CN)(2)].2H(2)O, [Ru(dbb)(2)(CN)(2)]-H2O, and [Ru(dbb)(2)(CN)(2)] emit luminescence at 640, 685, and 740 nm, respectively.