Observation of cascade f → d → f energy transfer in sensitizing near-infrared (NIR) lanthanide complexes containing the Ru(ii) polypyridine metalloligand

Abstract

Distinguishable d → f or f → d energy transfer processes depending on lanthanide ions are observed in isomorphous d–f heterometallic complexes containing the Ru(II) metalloligand (L_Ru), which lead to sensitized NIR emission (for Nd³⁺ and Yb³⁺) or enhanced red emission of L_Ru (for Eu³⁺ and Tb³⁺), and represent the first eye-detectable evidence of f → d energy transfer processes in Ln–Ru bimetallic complexes. Based on the systematic luminescence and decay lifetime study, cascade f → d → f energy transfer has been proposed in Ln1–Ru–Ln2 trimetallic systems for improved NIR sensitization.