Helicity switching in biological and artificial systems is a fundamental process that allows for the dynamic control of structures and their functions. In contrast to chemical approaches to responsive behaviour in helicates, the use of light as an external stimulus offers unique opportunities to invert the chirality of helical structures in a non-invasive manner with high spatiotemporal precision. Here, we report that unidirectional rotary motors with connecting oligobipyridyl ligands, which can dynamically change their chirality upon irradiation, assemble into metal helicates that are responsive to light. The motor function controls the self-assembly process as well as the helical chirality, allowing switching between oligomers and double-stranded helicates with distinct handedness. The unidirectionality of the light-induced motion governs the sequence of programmable steps, enabling the highly regulated self-assembly of fully responsive helical structures. This discovery paves the way for the future development of new chirality-dependent photoresponsive systems including smart materials, enantioselective catalysts and light-driven molecular machines.

A group of novel 2-(2′-hydroxyphenyl)benzothiazole derivatives (1−4) with excited-state intramolecular proton transfer (ESIPT) character were synthesized. Their photophysical properties were studied by means of steady-state absorption and fluorescence spectra and time-resolved emission method as well as theoretical calculation in a variety of solvents. All of these compounds can yield single fluorescence at the green region in nonpolar solvents such as n-hexane, while dual fluorescence consisting of the blue and green bands was captured in strong polar solvents like acetonitrile. In addition, a third emission band between the former two bands was detected for these molecules simultaneously with the blue and green ones generating the wellstructured triple fluorescence in protic solvent like ethanol. Systematical comparison of the fluorescence of these compounds in a series of solvents demonstrated that nonpolar solvents would facilitate ESIPT process and the green emission from the keto format, while the strong polar solvents impede the ESIPT process and favor the blue normal emission from enol. Protic solvents facilitate deprotonation and make the phenolic anion coexist with keto and enol and consequently lead to triple fluorescence. On the premise of identical keto emission intensity, the normal emission intensity of these compound increases consecutively in the order of increasing electron-withdrawing ability of the substituents regardless of solvents. The results of quantum-chemical calculations are well in line with the experimental spectra.