Chiroptical Switches: Applications in Sensing and Catalysis

Abstract

Chiroptical switches have found application in the detection of a multitude of different analytes with a high level of sensitivity and in asymmetric catalysis to offer switchable stereoselectivity. A wide range of scaffolds have been employed that respond to metals, small molecules, anions and other analytes. Not only have chiroptical systems been used to detect the presence of analytes, but also other properties such as oxidation state and other physical phenomena that influence helicity and conformation of molecules and materials. Moreover, the tunable responses of many such chiroptical switches enable them to be used in the controlled production of either enantiomer or diastereomer at will in many important organic reactions from a single chiral catalyst through selective use of a low-cost inducer: Co-catalysts (guests), metal ions, counter ions or anions, redox agents or electrochemical potential, solvents, mechanical forces, temperature or electromagnetic radiation.

Determination of Amino Acid Enantiopurity and Absolute Configuration: Synergism between Configurationally Labile Metal‐Based Receptors and Dynamic Covalent Interactions

“…[1] For this purpose, the use of supramolecular sensors is increasing and is usually combined with optical signaling techniques because they are rapid and often inexpensive. [2] In this context, particular interest has been directed toward the use of circular dichroism (CD). [3] This is due to the high information content conveyed by this technique and to the wide availability of sensitive CD instruments.…”

“…Ever growing interest in new and efficient stereoselective reactions requires the development of effective methods that allow accurate determination of the enantiomeric excess ( ee ) of reagents and products 1. For this purpose, the use of supramolecular sensors is increasing and is usually combined with optical signaling techniques because they are rapid and often inexpensive 2. In this context, particular interest has been directed toward the use of circular dichroism (CD) 3.…”

Supramolecular Chirality in Porphyrin Chemistry

“…Furthermore, these compounds have turned out to be particularly well suited for investigating different chiral processes and, particularly, supramolecular chirality, because of their specific and highly appropriate spectral, physico-chemical and synthetic characteristics, facile handling and superior propensity to form various supramolecular assemblies [2]. Furthermore, this kind of molecular and supramolecular system, so far, has attracted considerable attention of the scientific OPEN ACCESS community on account of the wide applicability in different fields of fundamental and applied sciences and modern technologies lying behind the judicious design of various chiroptical devices and sensors, molecular switches and machines, enantioselective materials and catalysts, as well documented in numerous reviews discussing these topics to a greater or lesser extent [3][4][5][6][7][8][9][10][11][12][13][14][15]. In general, chirality in the porphyrin-based supramolecular systems may be generated either via the intrinsic chiral modification of achiral porphyrinoids, by employing naturally occurring chiral pigments or via the external chiral field.…”

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.…”