Researchers at the Center of Green Chemistry and Catalysis in the Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences have received an issued Chinese invention patent for their preparation of photoresponse ionic liquids containing azobenzene moiety.

The photoresponsive ionic lquid is synthesized as follows: 4-(n-bromoalkylbenzene) azobenzene and alkylimidazole reacted in organic solvent in the dark. Organic solvent was removed in vaccum, after washing and drying, pure imidazole salt with anion (Br-) was obtained. Then the as resulted imidazole salt reacted with organic/inorganic salt containing target anion for 1 to 2 hours under dark conditions at room temperature. After filtration, filtrate condensation and drying, pure ionic liquid containing target anion was finally gained.

As expected, the azobenzene-based ionic liquids are characteristic of photoresponse, either in the solution or pure liquid state. For example, its UV absorption spectra and fluorescence emission spectra, and conductivity, can be reversibly tuned with the alternative UV or visible light irradiation.

As a special photochromic and conductive materials, these ionic liquids can be potentially used as information storage materials, materials for optical switching and optical devices and light-sensitive materials.

The patent is No. ZL200710307474.0.