Aggregation-induced near-infrared absorption of a pillar[5]arene trimer by charge transfer interaction

Abstract A series of pillar[5]arene receptors 1a-1d , containing mono-, bis- and tris-pillar[5]arene frames, are synthesized, and their host-guest complexation with 1,4-butanediamine•HCl ( BDH )and tris(2-aminoethyl)amine•HCl ( TAH ) are studied by NMR, UV–vis absorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Benzene-1,3,5-trispillar[5]arene 1a exhibits effective cooperativity and forms supramolecular polymers with electron acceptors BDH and TAH , respectively. Interestingly, driven by charge transfer interaction in 1a - BDH and 1a - TAH systems, a newly remarkable aggregation-induced absorption (AIA) in the visible to near IR regions (400–1100 nm) is observed. However, pillar[5]arenes 1b - 1d do not show such AIA character.