Solubility control of organic acid-base salts by photochromism

• A bisthienylethene with two phenanthroline rings formed precipitate with oxalic acid.
• Upon UV irradiation the precipitate dissolved while the solution became blue.
• By LC-DLS the diameter of solid particles was found to be several micrometers.
• By SEM, PXRD, DFT and DOSY the unit particle was found to have an ordered structure.
• After UV irradiation it cannot hold the ordered structure so that it dissolved.

The open form of a bisthienylethene with two phenanthroline groups at both ends of the molecule formed, upon the addition of oxalic acid, a sudden precipitation in solution. UV irradiation to the suspension induced dissolution of the precipitate together with the coloration of the solution. The chemical structure of the precipitate was investigated by low-coherence DLS, DOSY, SEM, powder XRD, and DFT calculations. Light of any wavelength is scattered when the bisthienylethene takes the open form structure while light with wavelengths longer than 800 nm is transparent for the closed form. We have, therefore, succeeded in constructing a photon-working aggregation-dissolution system which works as an optical shutter of the near-IR light as well as the prototype for the photon-working regulator of material concentration in solution.

Controlling the precipitation-dissolution behavior of organic salts was demonstrated by photochromism.Figure optionsDownload as PowerPoint slide