Regulating Copper‐Binding Affinity with Photoisomerizable Azobenzene Ligand by Construction of a Self‐Assembled Monolayer

Abstract

Photoactive molecules have attracted much interest because they allow molecular properties to be changed and switched dramatically. [1][2][3][4][5] For example, functional molecules and systems that both bind and release metal ions have been constructed by reversible structural regulation using photochromic molecules, such as spiropyran and azobenzene. [3, 4] In the case of a spiropyran derivative, one of the isomers bound a transition-metal ion through its negatively charged group, whereas the other isomer did not. This photoregulated metalbinding system was useful both in solution and in a polymer matrix.[3] However, the metal-binding ability was relatively weak since the binding site was singly negatively charged, and binding sites with two or more charged groups are required for a more effectively regulated metal-binding system.It has been reported that an azobenzene derivative containing two iminodiacetic acid moieties (azo-IDA) could strongly bind to a metal ion in aqueous solution, but the difference in the binding constants of the trans and cis isomers with the Cu II ion were relatively small: K Cu = 6.49 10 10