TETRANUCLEAR A-2',3'-C-3'',2''-H-2''',3'''-J]PHENAZINERUTHENIUM COMPLEX - SYNTHESIS, WIDE-ANGLE X-RAY-SCATTERING, AND PHOTOPHYSICAL STUDIES

The tetranuclear ruthenium complex {Ru[(tpphz)Ru(bpy)(2)](3)}(8+), whe re tpphz is ido[3,2-a:2',3'-c:3'',2''-h:2''',3'''-j]phenazine, has bee n synthesized by reaction of [Ru(tpphz)(3)](2+) with [Ru(bpy)(2)Cl-2] and by reaction of [Ru(bpy)(2)(tpphz)](2+) with [Ru(DMSO)(4)Cl-2]. The large distance between the chiral centers allows full H-1 NMR interpr etation despite the mixture of eight stereoisomers. The tetranuclear c omplex was further characterized by electrospray mass spectrometry and by the wide-angle X-ray scattering technique, which confirmed the sta rburst geometry. The photophysical properties of the tetranuclear comp lex in acetonitrile were studied and compared with those of [Ru(tpphz) (3)](2+) (1 x 10(-4) M acidic solution) and [(bpy)(2)Ru(tpphz)Ru(bpy)( 2)](4+) model molecules. The tetranuclear complex gives rise to a sing le emission, attributed to metal-to-ligand charge-transfer states invo lving peripheral Ru centers and tpphz bridging ligands.