Dual Modulation of a Molecular Switch with Exceptional Chiroptical Properties

Abstract

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.

Ruthenium‐Grafted Vinylhelicenes: Chiroptical Properties and Redox Switching

“…Few helicene‐based chiroptical switches have been described so far. They are either based on photochromic,4d–f redox,4a,c,g,h or acid–base4b,i,j systems. Furthermore, few other examples of electroactive helicene derivatives have been described in the literature 22.…”

Supra‐dendron Gelator Based on Azobenzene–Cyclodextrin Host–Guest Interactions: Photoswitched Optical and Chiroptical Reversibility

“…Light is one of the most important stimuli since it is easily controlleda nd is largely nondestructive. [21][22][23][24][25] In order to realize chiroptical switching based on azobenzene, it is important to transfer chirality to the azobenzene moiety,s ince azobenzene itself is achiral.D uring such chiral transfer,s elf-assembly of the component molecules is necessary.H owever,i nm any cases, although strong p-p interactions between azobenzene moieties can assist self-assembly, they often cause irreversibility of the trans-cis isomerization. Photochromic groups, such as azobenzene, spiropyran, or dithienylethene, have been incorporated into the gels through covalent bonds or by as upramolecular approach.…”

Intense redox-driven chiroptical switching with a 580 mV hysteresis actuated through reversible dimerization of an azoniahelicene

“…[5][6][7] Of particular interest are helicene-based switches, 8 since the exceptionally intense chiroptical properties 9-11 of helicenes could lead to a large increase in the magnitude of the differential chiroptical signal and such molecules have already been successfully exploited in technological applications. [12][13][14][15][16][17] In most cases, the switching of these helicenes through changes in electrochemical potential (redox switching) has been achieved via reduction or oxidation of electronically biased helicenes [18][19][20][21] or helicene-coordinated transition metals, [22][23][24][25][26] leading to strong chiroptical switching D(De) of up to 135 M À1 cm À1 (see Fig. 1A left) 21 and even chiroptical switching at wavelengths suitable molecular systems are based on simple, reversible redox reactions with little or no significant structural change of the helicene, 27 the difference between the ''ON'' and the ''OFF'' potentials (redox hysteresis) is small and on the order of 60 mV (e.g.…”