New luminescent Ru(II) complexes containing a dangling amine group, Ru(bpy)(2)(dien)(2+) and Ru(bpy)(2)(entn)(2+)

The complexes Ru(bpy)(2)(dien)(2+) (bpy = 2,2'-bipyridine, dien = 1,4,7-tri aza-heptane) and Ru(bpy)(2)(entn)(2+) (entn = 1,4,8-triazaoctane), which co ntain the Ru(bpy)(2) chromophore and a dangling amine group, have been prep ared and their chemical and physical properties were studied. To investigat e how the diamine ligand and the dangling amine influences the photophysica l properties of the Ru(bpy)(2) fragment, the complexes (Ru(bpy)(2)(en)(2+) (en = ethylenediamine), Ru(bpy)(2)(dmen)(2+) (dmen = N,N'-dimethylethylened iamine) and Ru(bpy)(2)(tmen)(2+) (tmen = N,N,N',N'-tetramethylethylenediami ne) have been synthesized and their properties compared with Ru(bpy)(3)(2+) . The configuration of the complexes in solution with a coordinating second ary amine was determined by NMR spectroscopy. The emission of the Ru(bpy)(2 )(diamine)(2+) complexes is quenched in basic solution (pH > 12) due to the deprotonation of the coordinating amine groups in the excited state. The a cid base reactions of the dangling amine have only little influence on the properties of the Ru(bpy)-chromophore. (C) 2001 Elsevier Science B.V. All r ights reserved.