Truxene-based columnar liquid crystals: self-assembled structures and electro-active properties

Columnar liquid-crystalline (LC) truxene derivatives containing branched flexible alkyl chains have been designed and synthesized. The dicyanomethylene and dithiafulvene substituents have been introduced into the pi-conjugated truxene framework to tune their electronic and redox properties as well as the molecular assembled structures. The pi-conjugated cores of dicyanomethylene- and dithiafulvene-appended truxenes adopt bowl-shaped conformations, giving rise to a large intrinsic dipole moment perpendicular to the aromatic framework. These molecules form stable columnar LC structures through intermolecular dipole-dipole interactions. The redox properties of LC truxene derivatives have been examined by cyclic voltammetry. The dicyanomethylene-appended truxene shows the reversible four-step electrochemical reductions, whereas the dithiafulvene-appended truxene undergoes three-step oxidations.