Mechanofluorochromism of Triphenylamine-BODIPY: Effect of twisted intramolecular charge transfer and restriction in rotation on fluorescence

The majority of the studies in field mechanofluorochromism (MFC), based on donor (D)-acceptor (A) complexes, have reported that MFC was strongly associated with intramolecular charge transfer (ICT) character and aggregation-induced emission (AIE). However, mechanism has been inconclusively demonstrated. In this study, a triphenylamine (TPA) introduced BODIPY complex designed synthesized to demonstrate D-A complex. We identified effect an external stimuli molecular geometry by employing solid state NMR, UV–vis spectroscopy, density functional theory (DFT) calculations; because geometry, depending stimuli, established as key for determining properties. relationship between properties experimentally investigated regard ICT restriction rotation (RIR) characteristics. Under stress, fluorescence quenching suppressed RIR, planarization-induced weak hypsochromically shifted spectrum. were not applied, occurred due freely rotating molecules; further, spectrum bathochromically strong induced high torsional angle D A.