Structure-property relationship in functionalized azobenzene photoswitches and their supramolecular behavior.

Abstract

Herein, we report the design, synthesis, and supramolecular behavior of 30 structurally diverse photoresponsive azobenzene molecular systems. To establish structure-property relationships, azobenzenes appended with N-picolinyl and/or N-benzyl groups tethered directly through carboxamides or via triazolylmethyl carboxamide linkages were explored. We have evaluated the photoswitching characteristics and thermal stability of the Z isomers through systematic studies. All the targets were also screened for their aggregation behavior and supramolecular aspects. Among all the derivatives, a few carboxamide-based systems formed microcrystals upon aggregation, showing light responsiveness. In contrast, the derivatives tethered via triazolylmethyl carboxamide linkage exhibited hydrogel formation with excellent water-absorbing capacity. All supramolecular aspects of the morphology of the microcrystal and hydrogel states and their stimuli-responsiveness have been studied using spectroscopy and various microscopic techniques.