Photoinduced Formation of an Azobenzene‐Based CD‐Active Supramolecular Cyclic Dimer

Abstract

A series of new photo-responsive amino acid-derived azobenzenedicarboxylic acid derivatives (S)-1 a-e were synthesized. Compound (S)-1 a in the trans form exhibited no circular dichroism (CD) signal in DMF under ambient conditions, whereas intense Cotton effects were observed upon UV irradiation, indicating the formation of a chiral supramolecular structure in the cis form. The CD signals disappeared when trifluoroacetic acid (TFA) was added to the solution. The ester counterpart [(S)-1 a'] showed no CD signal. Hydrogen bonding between the carboxy groups seemed necessary for constructing the supramolecular structure. The kinetic studies of cis to trans isomerization of (S)-1 a demonstrated that the formation of a chiral supramolecule enhances the stability of the cis-azobenzene structure. The ESI mass spectrum of stilbenedicarboxylic acid (S)-4, an analogue of (S)-1 b, confirmed the formation of a dimer. A theoretical CD study revealed that (S)-1 a in the cis form should be present as a cyclic chiral dimer.

Photo-Triggered Chiroptical Switching of Platinum Complexes Bearing Azobenzene Moieties

“…Recent systematic research of azobenzene-containing molecules and materials includes photoinduced/responsive 3D deformation, macromolecular assemblies at interfaces, orientation of liquid-crystalline polymers by surface segregation, macrocyclic molecular hinges, molecular devices, liquid crystalline polymeric actuators, and DNA nanomachines . Azobenzene derivatives featuring chiroptical activity enable control over the formation and decomposition of chiral supramolecules upon photoirradiation. − We have previously reported a chiral supramolecular formation system based on a bent cis -azobenzene unit …”

“…16−22 We have previously reported a chiral supramolecular formation system based on a bent cisazobenzene unit. 23 Platinum ethynyl complexes [Pt(PR 3 ) 2 (CC-Ar) 2 ] were first synthesized in the 1950s. 24,25 Pt(PR 3 ) 2 (CC-Ar) 2 derivatives are commonly stable and exhibit useful functions such as liquid-crystalline 26,27 and photoelectric properties.…”

Synthesis and Structure of Optically Active Oligo(N‐substituted‐m‐benzamide)s Bearing a Bithiophene Chromophore on the Benzene Ring

“…For these selected conformations, theoretical CD or absorption spectra were produced essentially according to refs. . Their electric transition and chiroptical parameters were computed on the ZINDO/S method in Gaussian 09W .…”

Amino‐Acid Based Chiral Trisubstituted Benzimidazole Supramolecules: Synthesis and Self‐Assembling Behavior

“…Nevertheless, TBIB derivatives that contain stereogenic centers have not been reported yet as far as we know, although they are expected to induce the formation of chirally regulated structures. We have previously reported a series of amino‐acid based chiral supramolecular systems stabilized by intra‐ and intermolecular hydrogen bonding interactions, and revealed their stimuli responsive structural changes [33–36] . Amino acids are simple chiral molecules having a variety of substituents, and able to undergo diverse reactions to produce a wide variety of chiral compounds.…”