[Ru(bpy)2(dppz-NH2)]2+ complex (dppz NH2: 7-amino-dipyrido [3,2-a:2′,3′-c]phenazine) as a useful photosensitizing unit for the construction of photoinduced energy transfer systems

7-Amino-dipyrido[3,2-a :2',3'-c]phenazine (dppz-NH2) has a diimine coordination site, a rigid and extended pi conjugation system, and a reactive amino group within the molecule, and [Ru(bpy)(2)(dppz-NH2)](2+) was synthesized as a useful photosensitizing unit fur the construction of photoinduced energy-transfer systems. Anthraquinone, anthracene, and [Os(bpy)(3)](2+) derivatives having a carboxylic acid function were used as energy-accepting units, and were successfully connected to [Ru(bpy)(2)(dppz-NH2)](2+) through an amide bond. Electronic spectral and electrochemical studies of the resultant complexes were carried out, and it was shown that effective excited electron or energy transfer took place from the Ru(II) polypyridyl center to these units. In the case of the heterodinuclear Ru(Il)/Os(II) complex, emission from the Ru(II) polypyridyl center was effectively quenched and that from the Os(II) polypyridyl center was increased compared to the reference Os(II) polyimine complex. The rate of energy transfer from the Ru(II) to the Os(II) polypyridyl center through the dppz-amide connector was estimated to be 1.0 x 10(8) s(-1) in acetonitrile.