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-triaza-heptane) and Ru(bpy)(2)(entn)(2+) (entn = 1,4,8-triazaoctane), which contain the Ru(bpy)(2) chromophore and a dangling amine group, have been prepared and their chemical and physical properties were studied. To investigate how the diamine ligand and the dangling amine influences the photophysical properties of the Ru(bpy)(2) fragment, the complexes (Ru(bpy)(2)(en)(2+) (en = ethylenediamine), Ru(bpy)(2)(dmen)(2+) (dmen = N,N'-dimethylethylenediamine) and Ru(bpy)(2)(tmen)(2+) (tmen = N,N,N',N'-tetramethylethylenediamine) have been synthesized and their properties compared with Ru(bpy)(3)(2+). The configuration of the complexes in solution with a coordinating secondary 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 acid 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 rights reserved.