Design of ligands to obtain lanthanide ion complexes displaying high quantum efficiencies of luminescence using the sparkle model

In this paper we exemplify how to use our sparkle model for the calculation of lanthanide complexes (SMLC-AM1-INDO/S-CI) together with Fermi's golden rule with the multipolar and exchange mechanisms to describe the ligand-lan thanide ion energy transfer for the purpose of designing ligands to obtain complexes displaying high quantum efficiencies of luminescence. Accordingly , we propose aromatic imides as efficient antennas and energy transfer liga nds when coordinated to Eu3+ ion. More specifically we designed Eu(btfai)(3 )bipy (btfai = benzoyltrifluoroacetylimide anion and bipy = bipyridine) and Eu(bzaci)(3)bipy (bzaci = benzoylacetylimide anion) which we then compare with their beta-diketone analogues Eu(btfa)(3)bipy (btfa = benzoyltrifluoro acetonate) and Eu(bzac)(3)bipy (bzac = benzoylacetonate), which have been p reviously synthesized and whose quantum efficiencies we have also previousl y measured. (Our theoretical results indicate that indeed the quantum effic iencies of Eu(btfai)(3)bipy and Eu(bzaci)(3)bipy are electronically equival ent to their highly luminescent beta-diketone analogues with the advantage of one less hydrogen directly bonded to the central atom of the beta-dicarb onylic anionic species. Indeed the possibility of vibronic coupling through that bond vibrational mode, which may be partially quenching the luminesce nce from the D-5(0) level of the Eu3+ ion in the beta-diketone analogues ca se, is thus eliminated. (C) 2000 Elsevier Science B.V. All rights reserved.