A photochromic salicylhydrazide based on perylene diimide and its application for ion sensor probes

Materials with photochromic properties have great potential for applications such as molecular switches, light-controlled materials, optical patterns, information storage, etc. Therefore, photochromic materials are urgently needed to meet the demand for such practical applications. Herein, a novel photochromic molecule perylene diimide salicyl hydrazide (PDISH) was synthesized, and its photochromic behavior and self-assembly properties were systematically studied. It exhibits reversible photo-controllable colour changes in the solution and solid states due to the excited-state intramolecular proton transfer (ESIPT) effect-coupled charge transfer (CT). Furthermore, the prominent morphological transition of PDISH from nanospheres to micro-rods occurred via self-assembly, rendering the fluorophores useable for monitoring and visualising the aggregation process. And the result of theoretical calculations of PDISH indicates that protons on nitrogen atoms have a significant effect on the fluorescence properties of PDISH. More interestingly, in the presence of Cu2+, the intramolecular hydrogen bonds of the compound were destroyed, resulting in rearrangement of its structure. Therefore, this PDISH has potential applications for Cu2+ detection. This study demonstrates that the PDISH compound is a multifunctional organic luminescent material that exhibits excellent photochromism, self-assembly, and ion probe properties.