Highly luminescent bis-diketone lanthanide complexes with triple-stranded dinuclear structure

Abstract

A new bis-β-diketone, 3,3′-bis(4,4,4-trifluoro-1,3-dioxobutyl)biphenyl (BTB), has been designed and prepared for the synthesis of a series of dinuclear lanthanide complexes [Ln₂(BTB)₃(C₂H₅OH)₂(H₂O)₂] [Ln = Eu (1), Gd (2)], [Ln₂(BTB)₃(DME)₂] [Ln = Nd (3), Yb (4); DME = ethylene glycol dimethyl ether] and [Eu₂(BTB)₃(L)₂] [L = 2,2-bipydine (5); 1,10-phenanthroline (6); 4,7-diphenyl-1,10-phenanthroline (7)]. Complexes 1–7 have been characterized by various spectroscopic techniques and their photophysical properties are investigated. X-ray crystallographical analysis reveals that complexes 1, 3 and 4 adopt triple-stranded dinuclear structures which are formed by three bis-bidentate ligands with two lanthanide ions. The complexes 1 and 3–7 display strong visible red or NIR luminescence upon irradiation at ligand band around 372 nm, depending on the choice of the lanthanide. The solid-state photoluminescence quantum yields and the lifetimes of Eu³⁺ complexes are determined and described.