Photoionization and trans-to-cis isomerization of β-cyclodextrin-encapsulated azobenzene induced by two-color two-laser-pulse excitation

Tatsuya Takeshita; Michihiro Hara

doi:10.1016/j.saa.2017.12.061

Photoionization and trans-to-cis isomerization of β-cyclodextrin-encapsulated azobenzene induced by two-color two-laser-pulse excitation

Spectrochim Acta A Mol Biomol Spectrosc. 2018 Mar 15:193:475-479. doi: 10.1016/j.saa.2017.12.061. Epub 2017 Dec 21.

Authors

Tatsuya Takeshita¹, Michihiro Hara²

Affiliations

¹ Department of Environmental and Food Sciences, Fukui University of Technology, Fukui, Japan.
² Department of Environmental and Food Sciences, Fukui University of Technology, Fukui, Japan. Electronic address: hara@fukui-ut.ac.jp.

PMID: 29289746
DOI: 10.1016/j.saa.2017.12.061

Abstract

Azobenzene (1) and the complex resulting from the incorporation of 1 with cyclodextrin (1/CD) are attractive for light-driven applications such as micromachining and chemical biology tools. The highly sensitive photoresponse of 1 is crucial for light-driven applications containing both 1 and 1/CD to reach their full potential. In this study, we investigated the photoionization and trans-to-cis isomerization of 1/CD induced by one- and two-color two-laser pulse excitation. Photoionization of 1/CD, which was induced by stepwise two-photon absorption, was observed using laser pulse excitation at 266nm. Additionally, simultaneous irradiation with 266 and 532nm laser pulses increased the trans-to-cis isomerization yield (Υ_t→c) by 27%. It was concluded that the increase in Υ_t→c was caused by the occurrence of trans-to-cis isomerization in the higher-energy singlet state (S_n), which was reached by S₁→S_n transition induced by laser pulse excitation at 532nm. The results of this study are potentially applicable in light-driven applications such as micromachining and chemical biology tools.

Keywords: Azobenzene; Cyclodextrin; Photoionization; Trans-to-cis isomerization; Two-color two-laser-pulse excitation.