Recently, a paper of Prof. Weihong Zhu group titled “Enabling Light Work in Helical Self-Assembly for Dynamic Amplification of Chirality with Photoreversibility” has been published on JACS as cover article (J. Am. Chem. Soc. 2016, 138, 2219−2224; http://pubs.acs.org/doi/abs/10.1021/jacs.5b11580), and spotlighted by JACS (http://pubs.acs.org/toc/jacsat/138/7, J. Am. Chem. Soc. 2016, 138, 2063−2063). In this work, a unique helical hydrogen-bonded self-assembly is reversibly photoswitched between photochromic open and closed forms upon irradiation with alternative UV and visible light.

    For years, chemists have taken inspiration from biology in the design of self-assembling, stimuli-responsive helical nanostructures. Such structures could provide insight into biological systems and enable the design of smart materials. Now, researchers led by Wei-Hong Zhu and Lifeng Chi describe a helical, hydrogen-bonded nanostructure that reversibly switches between open and closed forms in the presence of visible and UV light, respectively.

    The team reports the synthesis of the molecular precursors, which are composed of small organic building blocks based on dithienyl ethene with homo-chiral amino acid side chains. They characterize the self-assembled and thermally stable left- and right-handed super-helical nanostructures using microscopy, and find that the light-activated switching between open and closed forms is accompanied by a change in morphology, fluorescence, and helicity, reminiscent of biological systems such as protein and DNA. This demonstration of photoswitchable chiral amplification from small organic building blocks may serve as the basis for better understanding chiral communication between molecular and supramolecular chirality.
    The research was mainly completed by doctoral student, Yunsong Cai, under the direction of Prof. Weihong Zhu, and financially supported by National 973 Program (No. 2013CB733700), NSFC/China, NSFC for Distinguished Young Scholars (Grant No. 21325625).