Energy-Transfer Mechanisms in Ir-III-Eu-III Bimetallic Complexes

The bridging ligands in d-f bimetallic complexes play an important role in the excitation energy transfer (EET) process. To elaborate on the effect of the ligand on the EET process, a series of bridging ligands (-L), 1-(1,10-phenanthrolin-2-yl)-4,4,4-trifluorobutane-1,3-dione (phen3f), 1-(1,10-phenanthrolin-2-yl)-4,4,5,5,5-pentafluoropentane-1,3-dione (phen5f), 1-(2,2-bipyridine-6-yl)-4,4,4-trifluorobutane-1,3-dione (bpy3f), and 1-(2,2-bipyridine-6-yl)-4,4,5,5,5-pentafluoropentane-1,3-dione (bpy5f), and their corresponding iridium complexes, [(dfppy)(2)Ir(-L)] (dfppy=2-(4,6-difluorophenyl)pyridinato-N,C2), as well as their corresponding heteroleptic Ir-III-Eu-III complexes [{(dfppy)(2)Ir(-L)}(3)EuCl]Cl-2 were synthesized and characterized. Photophysical and kinetic results revealed that the alternation of the bridge ligand resulted in a systemic difference in the lowest triplet-state energy (T-1) of the iridium complexes, the EET efficiency from iridium complexes to the Eu-III ion, and a significant difference in the total luminescence quantum yields. Based on the nanosecond time-resolved phosphorescence spectra, a model for the energy-transfer mechanism was proposed for d-f bimetallic complexes, which indicated that the nonradiative relaxation of the excited energy of Eu-III, especially energy dissipation by means of the T-1 state, was the main reason for the discrepancy in the quantum yields of the four Ir-III-Eu-III complexes.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000322885600020&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Chemistry, MultidisciplinarySCI(E)1ARTICLE8852-8597