When size matters: exploring the potential of aminocyclopropenium cations as head groups in triphenylene-derived ionic liquid crystals in comparison with guanidinium and ammonium units

The influence of the size of a single ionic head group on the mesomorphic properties of hexaalkoxytriphenylenes was investigated by synthesising three derivatives with increasing head group diameter. The derivatives were investigated with optical polarising microscopy (POM), differential scanning calorimetry (DSC) and X-ray scattering (WAXS, SAXS). For the derivative with the small trimethylammonium head group, an enantiotropic mesophase was found. The derivative with the bigger tetramethylguanidine head group only showed a monotropic phase and the derivative with the largest bisdiisopropylaminocyclopropenium head group displayed no liquid crystaline properties at all. [GRAPHICS]