Excited state calculations of europium(III) complexes

A new theoretical methodology developed to guide the design of light-conversion molecular devices is applied to the complex tris(3-aminopyrazine-2-carboxylate)(1,10-phenanthroline) of Eu(III), and the results are compared to the experimental data obtained in our laboratory. The calculations have shown that there are two tripler states at 363 and 377 nm localized on the 1,10-phenanthroline, which are quasi-resonant with the (5)G(6) (374 nm) and L-5(6) (395 nm) energy levels of the Eu(III) ion, respectively. The 3-aminopyrazine-2-carboxylate anion ligands have a richer quasi-resonant energy level structure, namely, three singlet states (344, 323 and 377 nm) and their corresponding triplet states (498, 509 and 530 nm), which are near-resonant to the D-5(4) and D-5(0) Eu(III) energy levels, respectively. These ligand and metal ion energy levels were used in the dipole-dipole and dipole-2'-pole models for energy transfer rate calculations. Thus, the high quantum yield observed for this complex (28% in DMSO solution) seems to be due to the calculated high yield energy transfer from these several ligand states to the quasi-resonant Eu(III) energy levels.