Spectra, energy levels, and energy transition of lanthanide complexes with cinnamic acid and its derivatives

Abstract High resolution spectra and luminescent lifetimes of 6 europium(III)–cinnamic acid complex {[Eu 2 L 6 (DMF)(H 2 O)]·nDMF·H 2 O} m (L = cinnamic acid I , 4-methyl-cinnamic acid II , 4-chloro-cinnamic acid III, 4-methoxy-cinnamic acid IV , 4-hydroxy-cinnamic acid V , 4-nitro-cinnamic acid VI ; DMF = N, N-dimethylformamide, C 3 H 7 NO) were recorded from 8 K to room temperature. The energy levels of Eu 3 + in these 6 complexes are obtained from the spectra analysis. It is found that the energy levels of the central Eu 3 + ions are influenced by the nephelauxetic effect, while the triplet state of ligand is lowered by the p–π conjugation effect of the para-substituted functional groups. The best energy matching between the ligand triplet state and the central ion excited state is found in complex I . While the other complexes show poorer matching because the gap of 5 D 0 and triplet state contracts.