Photoinduced formation of an azobenzene-based CD-active supramolecular cyclic dimer

Hiromitsu Sogawa; Kayo Terada; Yu Miyagi; Masashi Shiotsuki; Yoshihito Inai; Toshio Masuda; Fumio Sanda

doi:10.1002/chem.201406054

Photoinduced formation of an azobenzene-based CD-active supramolecular cyclic dimer

Chemistry. 2015 Apr 27;21(18):6747-55. doi: 10.1002/chem.201406054. Epub 2015 Mar 12.

Authors

Hiromitsu Sogawa¹, Kayo Terada, Yu Miyagi, Masashi Shiotsuki, Yoshihito Inai, Toshio Masuda, Fumio Sanda

Affiliation

¹ Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura Campus, Nishikyo-ku, Kyoto 615-8510 (Japan); Present Address: Department of Organic and Polymeric Materials, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8552 (Japan).

PMID: 25766581
DOI: 10.1002/chem.201406054

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.

Keywords: UV/Vis spectroscopy; amino acids; hydrogen bonding; photoresponsiveness; supramolecular chemistry.