Ruthenium(ll)Complexes Containing 8-(Dimethylphosphino)quinoline(Me_2Pqn):Preparation,Crystal Structures,and Electrochemical and Spectroscopic Properties of [Ru(bpy or phen)_(3-n)(Me_2Pqn)_n](PF_6)_2(bpy 2,2/-Bipyridine;phen=1,10-Phenanthroline;n=1,2

摘要

Several new ruthenium(ll)complexes containing 8-(dimethylphosphino)quinoline(Me_2Pqn)were synthesized,and their structures and electrochemical/spectroscopic properties have been investigated.In addition to the mono-(Me_2Pqn)complex [Ru(bpy or phen)_2(Me_2Pqn)](PF_6)_2(1 or 1';bpy=2,2'-bipyridine;phen=1,10-phenanthroline),the geometrical isomers trans(P)-and Ci-[Ru(bpy)(Me_2Pqn)_2](PF_6)_2(tP-2 and C,-2)and mer-and fac-[Ru(Me_2Pqn)_3](PF_6)a(m-3 and f-3)were also selectively synthesized and isolated.It was found that complexes tP-2 and m-3 were converted quantitatively to the corresponding d-2 and f-3 isomers,respectively,by irradiation of light corresponding to the MLCT transition energy.The strong trans influence of the Me_2P-donor group of Me_2Pqn was confirmed by the X-ray structural analyses for 1,tP-2,m-3,and f-3.Cyclic voltammetry of a series of complexes,[Ru(bpy)_3l(PF_6)_2,1,C_1-2,and f-3,exhibited a reversible one-electron oxidation wave and two or three one-electron reduction waves.The oxidation potentials of the complexes gave a large positive shift with increasing number of coordinated Me_2Pqn molecules,indicating a larger pi-acceptability of the Me_2P-group compared with bpy or qn.Complex f-3 in EtOH/MeOH(4:1)glass at 77 K exhibited an intense long-lived(r=920 mus)emission arising from the quinoline-based ~3(pi-pi)excited state.In contrast,the mixed-ligand complexes 1,1',and d-2 showed a characteristic dual emission,giving a double-exponential emission decay,and the dual emission originates from both the bpy-based ~3MLCT and the quinoline-based ~3(pi-pi)emitting states.