Dual modulation of a molecular switch with exceptional chiroptical properties.

The ability to modulate the chiroptical properties of optically active molecules induced by external stimuli such as light, heat, and electrical fields allows for the design and development of molecular switches, memory devices, sensors, and photonic devices. A helical o-terphenyl compound functionalized with photoresponsive azobenzene and electroactive imide groups is designed as a dual-mode chiroptical molecular switch. Its exceptional optical activity (e.g., [alpha]436 = -9500) can be changed and modulated through photoisomerization of the azobenzene moiety using UV and visible light. Reversible modulation by electrochemical means was also achieved through the redox reaction occurring at the imide group. Large chiroptical read-out signals were observed during the redox cycles as indicated by the molar ellipticity values as high as 285,000 deg.cm2.dmol-1. Exceptionally high optical activity and large responses to both light and electrical bias make this chiral molecule suitable for the development of new molecular switches, sensors, and other optical devices.