Viscosity-induced dual-emission of europium ions containing metallopolymer

Abstract A hybrid structure poly[(9,9′-dihexyl-9H-fluoren-2,7-yl)-6,6′-(2,2′:6,2″-terpyridine)] complexed with europium tris[3-trifluorometyhydroxymethylene]-(+)-camphorate, with luminescence sensitive to viscous chemical environments is presented. Four solvents were tested: chloroform, toluene, DMF and DMSO. The material depicts a dual-emission profile with red luminescence from europium ions in the DMF and DMSO media, whereas in chloroform and toluene solution the structure presents blue emission only. In this study, absorption, excitation, emission and lifetime measurements are presented and discussed. It is suggested that DMSO and DMF restrict intramolecular motion / rotation on the polymer backbone, minimizing non-radioactive energy losses and promoting the europium luminescence via aggregation–induced emission (AIE), caused by the viscous environments.