Three-in-one: dye-volatile cocrystals exhibiting intensity-dependent photo-chromic, photo-mechanical and photo-carving response

30 November 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Cocrystallization of a cis-azobenzene dye with volatile cocrystal former molecules, such as pyrazine and dioxane, leads to materials that exhibit at least three different light intensity-dependent responses upon irradiation with low-energy visible light. Specifically, the halogen bond-driven assembly of cis-(p-iodoperfluorophenyl)azobenzene with volatile halogen bond acceptors produces cocrystals whose light-induced behaviour varies significantly depending on the intensity of the light applied. Low-intensity (<1 mW∙cm-2) light irradiation leads to a colour change due to low levels of cis-trans isomerization. Irradiation at higher intensities (150 mW∙mm-2) produces photo-mechanical bending, caused by more extensive azo dye isomerization. At still higher irradiation intensities (2.25 W∙mm-2) the cocrystals undergo photo-carving, i.e. they are readily shaped, punctured, and cut with micrometer precision using laser light. This work demonstrates how the recently reported photo-carving behaviour can be combined with different types of photo-responses, providing a design for multi-responsive materials that can respond to different levels of irradiation with optical colour change, photo-mechanical bending, or photo-carving, as laser power is increased.


Halogen bonding
Crystal Engineering

Supplementary materials

Electronic Supplementary Information
Detailed information on design of experiments, and selected results of analysis by UV-Vis spectroscopy, single crystal X-ray diffraction, NMR spectroscopy, Raman spectroscopy, scanning electron microscopy, high-speed camera recordings, thermal analysis and theoretical calculations.


Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.