Light-Modulated Morphological Transformation of Spiropyran Derivative from Nanosphere to Nanorod.

The construction of tunable morphological systems has important implications for understanding the mechanism of molecular self-assembly. In this study, we report a spiropyran derivative M1 with light-responsive assembly morphology, which can be tuned from nanosphere to nanorod by ultraviolet light irradiation. The absorption spectra show that M1 molecules are transformed from closed-ring (SP) isomers into open-ring (MC) isomers and start to form H-aggregates with increasing irradiation time. Density functional theory calculations indicate that MC-MC isomers possess stronger binding energy than SP-SP isomers. The MC isomers may thus facilitate the dissociation of the SP-SP aggregates and promote the change of self-assembled morphology with the aid of stronger π-π stackings and dipole-dipole interactions. Our research gives an effective method for modulating the morphology of assemblies, with great potential for applications in smart materials. This article is protected by copyright. All rights reserved.