Highly efficient sensitized red emission from europium (III) in Ir-Eu bimetallic complexes by 3MLCT energy transfer

Two novel iridium-europium bimetallic complexes, {[(dfppy)(2)Ir(mu-phen5f)](3)EuCl}Cl-2 and (dfppy)(2)Ir(,mu-phen5f)Eu(TFAcA)(3) [dfppy represents 2-(4',6'-difluorophenyl)-pyridinato-N,C-2', phen5f stands for 4,4,5,5,5-pentafluoro-1-(1',10'-phenanthrolin-2'-yi)-pentane-1,3-dionate and TFAcA represents trifluoroacetylacetonate], were successfully synthesized. The novel ligand Hphen5f with four coordination sites was designed as a bridge to link the Ir-III center and the Eu-III center. The X-ray diffraction data shows that the nonbonding distances for Eu... Ir are 6.028, 5.907, and 6.100 A in the bimetallic complex {[(dfppy)(2)Ir(mu-phen5f)](3)EuCl}Cl-2, Photophysical studies implied that the high efficient red luminescence from the Eu-III ion was sensitized by the (MLCT)-M-3 (metal-to-ligand charge transfer) energy based on an Ir-III complex-ligand in a d-f bimetallic assembly. The excitation window for the new bimetallic complex {[(dfppy)(2)Ir(mu-phen5f)](3)EuCl}Cl-2 extends up to 530 nm (1 x 10(-3) M in EtOH), indicating that this bimetallic complex can emit red light under the irradiation of sunlight.