Orthogonally Incorporating Dual-Fluorescence Control into Gated Photochromism for Multifunctional Molecular Switching.

Gated photochromism is of interest for the operation and control of modern high-tech optofunctional materials. For further advancing this topic towards the achievement of multifunctional molecular switching, however, it remains a great challenge to incorporate multiple fluorescence regulation into gated photochromism in one unimolecular system. Herein, it is reported that a dithienylethene derivative DTEN with a Schiff base connection can be facilely synthesized by one-step coupling, and it enabled distinct color and spectral changes upon different stimuli, including ultraviolet, visible light, Ni , and Al . Relying on hydrazine and hydroxy units in this molecule, compound DTEN exhibited novel Ni -locked photochromic characteristics originating from complexation of the compound with Ni in a 2:1 stoichiometry. On the other hand, a 1:1 complexation between compound DTEN and Al could allow both of the initial and photostationary states of DTEN to display fluorescent enhancement and a redshift, realizing a dual-fluorescence "turn-on" sensing of Al by light. On this basis, it is argued that the switching of the coordination mode between DTEN and Ni or Al brings up the possibility of tunable photoswitching by multiple stimuli, which offers a novel way for future development of multifunctional switching materials with different input and output signals, as exemplified by the construction of a delicate molecular circuit.