Long-Lived MLCT Excited States-Ru~II Complexes with a Helical Bis-Phen Ligand

摘要

The synthesis of a new RU~II complex [Ru(L_1)(4,7-dppen)]~2+,bearing a ttradentate bis-1,10-phenanthroline ligand L_1,is described.X-ray crystal structure analysis shows that the tetradentate ligand L_1 coils around the metal and occupies both eaxial and two of the equatorial positions of the complex.~1HNMR studies clearly indicate that the complex has C_2 symmetry in solution.the room temperature luminescence properties of [Ru(L_1)(4,7-dpphen)]~2+ have been studied,as have those of the related complex [Ru(L_2)(4,4'-dmbp)]~2+.For both complexes,theluminescence quantum yields and life-times are three to ten times higher than those of [Ru(bpy)_3]~2+.These unusual results are explained by the geometrical constraints imposed by the tetradentate ligands L_1 and L_2 in their respective complexes,resulting in an effective decoupling between the ~3MLCT and ~3MC excited states.