An unexpected non-conjugated AIEgen with a discrete dimer for pure intermolecular through-space charge transfer emission

Abstract

Manipulation of the charge transfer in donor-acceptor-type molecules is essential for the design of controllable aggregate luminescent materials. Apart from the traditional through-bond charge transfer (TBCT) systems which suffer from complicated structural design, poor tunability and low quantum efficiency, through-space charge transfer (TSCT) has been proved as an alternative yet facile strategy in tuning photophysical processes. In this work, by simply changing nucleophilic reaction bases, a traditional conjugated acrylonitrileAP1and an unexpected non-conjugatedAP2with a carboxamide-functionalized oxirane linker could be obtained. The long-range π-π stacking in conjugatedAP1results in mixed intramolecular TBCT plus intermolecular TSCT emission. However, facilitated by the steric hindrance effect of the big oxirane connector and the unique discrete dimer packing, non-conjugatedAP2exhibits pure and efficient intermolecular TSCT emission in both aggregate and crystalline states. The flexibility of the non-conjugated character further leads to better reversible stimuli-responsiveness to mechanical force forAP2than for the rigidAP1.