Aggregation-induced white-light emission from the triple-stranded dinuclear Sm(iii) complex

Abstract

A novel bis-β-diketone ligand, 4,4′-bis(4,4,4-trifluoro-1,3-dioxobutyl)(phenoxy)-1,1′-binaphthalene (BTPB), is designed for synthesis of a white light emissive lanthanide complex. The ligand bears two benzoyl β-diketonate sites linked by a 1,1′-binaphthoxy spacer. Reaction of the doubly negatively charged bis-bidentate ligand with lanthanide ions forms triple-stranded dinuclear complexes Sm₂(BTPB)₃(H₂O)₄ (1) and Gd₂(BTPB)₃(H₂O)₄ (2), which have been fully characterized by various spectroscopic techniques. UV-Vis absorption and emission spectroscopic techniques are used to investigate photophysical properties of the ligand and its complexes in THF and CHCl₃. In some cases aggregation of the ligand results in the appearance of a new luminescence band at about 510 nm in addition to the monomer fluorescence. In complex 1, partial energy transfer from BTPB results in Sm(III)-based red light emission in addition to the BTPB-based blue/green emission. With the variation of the excited wavelength and concentration of the solution, complex 1 shows a tunable white light emission with the balance of three primary colors. This is an unusual case of observation of white light emission from a single molecule Sm(III) complex.