Photoalignment and surface-relief-grating formation are efficiently combined in low-molecular-weight halogen-bonded complexes

It is demonstrated that halogen bonding can be used to construct low-molecular-weight supramolecular complexes with unique light-responsive properties. In particular, halogen bonding drives the formation of a photoresponsive liquid-crystalline complex between a non-mesogenic halogen bond-donor molecule incorporating an azo group, and a non-mesogenic alkoxystilbazole moiety, acting as a halogen bond-acceptor. Upon irradiation with polarized light, the complex exhibits a high degree of photoinduced anisotropy (order parameter of molecular alignment > 0.5). Moreover, efficient photoinduced surface-relief-grating (SRG) formation occurs upon irradiation with a light interference pattern, with a surface-modulation depth 2.4 times the initial film thickness. This is the first report on a halogen-bonded photoresponsive low-molecular-weight complex, which furthermore combines a high degree of photoalignment and extremely efficient SRG formation in a unique way. This study highlights the potential of halogen bonding as a new tool for the rational design of high-performance photoresponsive suprastructures. An unprecedented optical performance is reported for a novel photoresponsive supramolecular liquid-crystalline complex, self-assembled through halogen bonding between a non-mesogenic stilbazole derivative, acting as a bond acceptor, and a non-mesogenic bond donor containing an azo-group. Efficient photoalignment and an exceptional surface-relief-grating formation are combined in this low-molecular-weight supramolecular assembly, thanks to the high directionality of the halogen bond. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.