Tunable aggregation-induced emission, solid-state fluorescence, and mechanochromic behaviors of tetraphenylethene-based luminophores by slight modulation of substituent structure

Abstract

Herein, we report the synthesis of two AIE-active tetraphenylethene-derived luminogens with diethylamino (TPEDA) or pyrrolidino group (TPEPL) as terminal substituents, and systematically investigate the influence of diethylamino and pyrrolidino groups as terminal substituents on their photophysical properties and mechanochromic behavior. Single-crystal structural analyses verified that the free alkyl chains of the diethylamino groups were beneficial to loosen the intermolecular stacking. They exhibited distinct luminescence behaviors in the aggregated state. Compared with TPEDA, TPEPL displayed a long-wavelength solid-state fluorescence due to the more extended π-conjugation system across its intermolecular packing structure. However, TPEDA exhibited mechanochromic behavior that manifested in a larger red-shift (25 ​nm), which was attributed to its looser stacking mode. The work not only presents a better understanding of structure-property relationship, but also offers a new method for modulating intermolecular stacking and developing mechanochromic materials.