A Chiroptical Molecular Switch with Distinct Chiral and Photochromic Entities and Its Application in Optical Switching of a Cholesteric Liquid Crystal

Abstract

A chiroptical molecular switch with distinct chiral and photochromic entities and its application in optical switching of a cholesteric liquid crystal van Delden, R.A.; Mecca, T.; Rosini, C.; Feringa, B.L.

The Control of the Cholesteric Pitch by Some Azo Photochemical Chiral Switches

“…This was somehow unexpected as very careful measurements of 6,6'-dimethoxy-5,5'-bis(benzeneazo)-2,2'-diethoxy-1,1'-binaphthalene showed no variation of this couplet upon photoisomerisation. [15] To gain a better insight into this phenomenon, the reverse isomerisation process was followed starting with the pure ZZ isomer (obtained by TLC separation). [29] The amplitude of the exciton couplet is comparable to that of the EE isomer and upon irradiation with visible light also decreases.…”

“…With two exceptions, [14,15] in which azobenzene photochromism was combined with the axial chirality of binaphthyl, the few cases that have been investigated have dealt with azobenzenes with more or less traditional pendant groups with central chirality attached in various positions; [16,17] these compounds are characterised by low-to-medium twisting powers. Very recently Kato and co-workers reported a photoresponsive chiral gelator based on 1,2-bis(acylamino)cyclohexane.…”

“…This behaviour is quite unusual, and, to our knowledge, only one example of photocontrolled-handedness inversion of nematic phases doped with only a chiral photochemical switch has been reported. [15] Several other examples of photochemical switching of cholesteric handedness have been reported in the literature (see for example ref. [33]), however, in no case is the chiral photoswitch the only chiral additive in the system.…”

Supramolecular Structure of Extrinsically Chiral Porphyrin Hetero‐Assemblies and Achiral Analogues

“…But chirality is also receiving growing interest for the possible technological applications that span from chiroptical devices [1] to asymmetric catalysis, [2] memory systems, [3,4] and others.[5]The transfer of chiral information to achiral molecules through non-covalent interactions, expressed at a supramolecular level, has, in particular, gained great consideration. [6,7] In fact, non-covalent synthesis, especially when molecular recognition and self-assembly processes are involved, [8] presents many advantages: i) it is not time consuming, ii) it does not lead to side products, and iii) it dose not require an external energy source for reaction.…”

“…But chirality is also receiving growing interest for the possible technological applications that span from chiroptical devices [1] to asymmetric catalysis, [2] memory systems, [3,4] and others. [5] The transfer of chiral information to achiral molecules through non-covalent interactions, expressed at a supramolecular level, has, in particular, gained great consideration.…”