A new TPE-based tetrapodal ligand and its Ln(iii) complexes: multi-stimuli responsive AIE (aggregation-induced emission)/ILCT(intraligand charge transfer)-bifunctional photoluminescence and NIR emission sensitization

Abstract

A tetrapodal zwitterionic-type ligand featuring both AIE (aggregation-induced emission) and ILCT (intraligand charge transfer) properties, namely 1,1′,1′′,1′′′-(4,4′,4′′,4′′′-(ethene-1,1,2,2-tetrayl)tetrakis(benzene-4,1-diyl))tetrakis(methylene)tetrapyridin-4(1H)-one (TPE-4PO) has been designed and applied to the assembly of lanthanide complexes LIFM-21(Ln) (Ln = Sm, Eu, Gd, Tb and Dy). Apart from sensitization of NIR emission of Sm³⁺ and Dy³⁺, the resulting ligand and lanthanide complexes show both AIE and ILCT-related photoluminescence behaviors. The photo-response of this system to different aggregation states, solvents’ polarity and mechanical grinding was demonstrated by distinguishable emission intensities and colours.