Ionic liquid crystals based on a triscatecholatotitanate(IV) complex associated with imidazolium counter-ions

The triscatecholatotitanate(IV) anion (Ti(Cat)32-) interacts with various imidazolium cations (2-7) to generate salts (A-F) where the titanium dianion complex is associated with two imidazolium monocations. Two types of cation form these salts; species 2-4 bear methoxy groups, whereas one, two or three dodecyl linear alkyl chains are incorporated within 5, 6 and 7, respectively. These salts were characterized in solution by ¹H NMR and the crystal structure of salt C containing the complex Ti(Cat)32- with two imidazolium cations substituted by two methoxy groups (3) was established. Differential scanning calorimetry (DSC) measurements and polarized optical microscopy (POM) observations attest to the thermotropic liquid crystal behavior of the salts, where long alkyl chains are present in salts containing imidazolium cations (5-7). The data extracted from the small- and wide-angle X-ray scattering (SWAXS) analysis of salts 5-7 enable the proposal of the supramolecular organisations of the three mesophases. This organisation is dependent on the number of alkyl chains that compose the imidazolium cations.