A simple AIE-active salicylideneaniline towards bimodal encryption-decryption with unique ESIPT-inhibited amorphous state

Multimodal encryption-decryption with photochromism has been proved to ensure information security with great feasibility and operability. However, most of the photochromic materials are applied in single-mode encryption-decryption and highly dependent on crystallization, requiring long manufacturing time and lacking of controllability. Hence, amorphous materials with simple preparation and bimodal encryption-decryption are of good alternates. Herein, we have succeeded in developing an aggregation-induced emission-active and photochromic ATPA-SAB with crystalline form via introduction of the propeller-like and bulky triphenylamine (TPA). Expectedly, the amorphous materials can be obtained by fast precipitation. Examining its amorphous structures, the intramolecular N‧‧‧H distances of around 4.000 Å is largely over the normal intramolecular hydrogen bond of circa 1.800 Å, impeding the intrinsic excited-state intramolecular proton transfer process (ESIPT) for the first time, hence prohibiting photochromism. This work not only provides a strategy to construct amorphous materials and inhibit ESIPT process with TPA, but also applies both crystalline and amorphous materials for bimodal encryption-decryption to upgrade information security.