“Catch-and-release” of porphyrins by photoswitchable self-assembled monolayers

Abstract

A novel cationic, photoresponsive azobenzene derivative with the characteristic of self-assembly, 2-{4-[(E)-(4-{[11-(dodecylthio)undecyl]oxy}phenyl)diazenyl]phenoxy}-N,N,N-trimethylethanaminium bromide (1), has been synthesized. Self-assembled monolayers (SAMs) of 1 on ultrathin, transparent platinum electrodes have been fabricated and the reversible trans ⇆ cis interconversion has been demonstrated by absorption spectroscopy in transmission mode and contact angle measurements. It is shown that such photoresponsive SAMs promote the binding of anionic porphyrins at the metal surface and trigger their release upon light excitation exploiting the different light-controlled electrostatic interactions with the two isomeric forms of 1.