Dual-Gated Photochromism for Both Directions of Azobenzene Isomerization via Metal Complexation

Abstract

A macrocyclic ligand bearing two azobenzene and two terpyridine units forms dinuclear metal complexes that control photoisomerization through metal complexation. The trans complex suppresses trans-to-cis isomerization, whereas the cis complex is completely inert to light and heat, demonstrating dualgated photochromism of both azobenzene isomers.Photochromic compounds have been extensively utilized in a variety of fields, including molecular machines, biology, materials science, and catalysis, because photoisomerization induces drastic geometrical and electronic changes associated with the ON/OFF switching of various functions. 1-3 More recently, the development of "locked photochromism" (or gated photochromism)-photochromism that can be switched ON or OFF by external stimuli-has attracted considerable attention for the construction of multi-stimuli-responsive systems, which are expected to be applied to molecular logic gates and multi-input molecular machines. 4-9 Significant efforts have therefore been devoted to producing gated photochromism by controlling the photoreactivity of photochromic compounds.