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, Ni2+ , and Al3+ . Relying on hydrazine and hydroxy units in this molecule, compound DTEN exhibited novel Ni2+ -locked photochromic characteristics originating from complexation of the compound with Ni2+ in a 2:1 stoichiometry. On the other hand, a 1:1 complexation between compound DTEN and Al3+ 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 Al3+ by light. On this basis, it is argued that the switching of the coordination mode between DTEN and Ni2+ or Al3+ 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.