An ionic liquid (IL) composed of 9-anthracenecarboxylate anion and ammonium cation possessing three diethylene glycol chains shows phototriggered dimerization of anthracence chromophores. It causes segregation and crystallization of protonated 9-anthracenecarboxylic acid dimer, which is associated with the concurrent liberation of the free amine in the IL. This work provides a new molecular design for photoresponsive ILs, whose first application for site-selective photopatterning is demonstrated.Ionic liquids (ILs) have attracted considerable interest from many researchers because of their unique physical and chemical properties, which are tunable depending on their constituents.
13One of the evolving areas in this field is the introduction of mesoscopic interfaces 4,5 for developing novel interfacial phenomena. 6,7 In this regard, ILs containing π-conjugated chromophores are attractive as photofunctional soft materials that show new applications such as condensed luminescent materials 810 and solar thermal storage. 11 We have recently reported the photoliquefaction of ionic crystals to ILs by employing cationic azobenzene derivatives covalently modified with three flexible diethylene glycol chains in the ammonium head group. 11 Photon energy was effectively stored not only as the conformational energy of the azobenzene unit but also as the latent heat of crystallization, where the integration of self-assembly phenomena and photoresponsive ILs opened the doors to the phase crossover chemistry.
11Here, we describe a new photoresponsive IL that shows photoinduced crystallization phenomena. It is formed from a well-known Brønsted acid (9-anthracenecarboxylic acid, A-COOH) 12,13 and a Brønsted base having three flexible diethylene glycol chains (tris[2(2methoxyethoxy)ethyl]amine, 1). This integration based on acidbase neutralization gives a chromophoric IL [1-H] +