Cu²⁺-Selectivity gated photochromism in Schiff-modified diarylethenes with a star-shaped structure

A great deal of effort has been devoted to developing gated photochromic systems due to their advantages in the smart materials and opto-electronic fields, whereas the gating function through certain ions has rarely been addressed. Since the photochromic materials gated by ions can be readily further processed into a multi-functional molecular switch and probe, we herein designed and conveniently synthesized a star-shaped Schiff-based diarylethene derivative showing typical photochromic properties in solution. This compound possesses two response channels (colorimetric and fluorogenic) to Cu²⁺ ions with photoswitching characteristics, making it a viable photochromic probe. It is noteworthy that its photochromic reactivity can be locked when Cu²⁺ ions are introduced into the solution. Moreover, the photoinactive and photoactive states can be interchanged reversibly by binding Cu²⁺ ions and unbinding Cu²⁺ ions using EDTA, which shows promise for application in multi-controlled molecular switches and smart materials. The mechanism of the photochromic properties locked by Cu²⁺ ions is reasonably proposed by theoretical simulations. These results could be valuable for the further development of molecular switching systems with multiple stimuli responses.