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

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 266 nm. Additionally, simultaneous irradiation with 266 and 532 nm laser pulses increased the trans-to-cis isomerization yield ((sic)(t) (-> c)) by 27%. It was concluded that the increase in (sic)(t) (-> c) was caused by the occurrence of trans-to-cis isomerization in the higher-energy singlet state (S-n), which was reached by S-1 -> S-n transition induced by laser pulse excitation at 532 nm. The results of this study are potentially applicable in light-driven applications such as micromachining and chemical biology tools. (C) 2018 Elsevier B.V. All rights reserved.