Janus luminogens with bended intramolecular charge transfer: Toward molecular transistor and brain imaging

The ingenious construction of electron donor-acceptor (D-A) systems has been proven to be the major trend for advanced performance optoelectronic materials. However, the related development is undiversified and has become stereotyped in recent years, and the explorations of innovative architecture with both prominent optoelectronic properties and innovatively coined optoelectronic mechanisms are appealing, yet significantly challenging tasks. Here, we exploit a series of unique Janus luminogens, namely TAOs, with unique charge separation in a simple five-membered mesoionic ring. TAOs, having low molecular weight (∼329 g mol⁻¹), present efficient aggregation-induced red/near-infrared emission (550–850 nm) with up to 21.5% of fluorescence quantum yield. An original mechanism, termed bended intramolecular charge transfer (BICT), is proposed to understand the fluorescence behavior. It is experimentally demonstrated that TAOs exhibit great potential for use as molecular transistors and can be efficiently utilized in living cells, bacteria, and brain imaging in a straightforward manner by using intravenous postinjection with outstanding photostability and biocompatibility.