Donor-acceptor typed aggregation-induced emission luminophores based on 1,1-dicyanomethylene-3-indanone unit for bridge-dependent reversible mechanochromism and light-up biosensing of hypochlorite

Three donor-acceptor typed AIE-active molecules TPEThIC, TPEPhIC and TPEIC with the same tetraphenylethene and 1,1-dicyanomethylene-3-indanone (IC) but with the different spacers of thiophene ring, benzene ring and direct single bond between TPE and IC units were designed and synthesized. The modulation of these spacers caused the variations of electron cloud distribution, spatial conformation and molecular packing architecture, resulting in the distinctions of photophysical properties, response towards external mechanical grinding and the performance of fluorescent sensing hypochlorite. In terms of red-shift AIE emission, TPEIC with more twisted conformation possesses higher relative intensity (I/I0) than the others in THF-H2O mixture. Moreover, the modifying of π-conjugated spacer provided molecules with inverse mechano-responsive behaviors, where TPEIC and TPEPhIC exhibited a 117 nm red-shift emission and a 29 nm blue-shift emission respectively. Additionally, based on IC moiety as a receptor of hypochlorite (ClO-), the three molecules were qualified with light-up fluorescent sensing ClO- with obvious visible color changes. The biosensing of endogenous ClO- based on better detection performance of TPEIC probe was achieved in HeLa cells. These results demonstrate that the great potential of IC as a strong electron-deficient unit for designing donor-acceptor typed mechano-responsive materials and light-up biosensors for detection of hypochlorite in living cells.