Résumé : We describe a practical synthesis of octaalkoxycarbonyl phthalocyanines that are well soluble in various organic solvents and form liquid crystalline columnar mesophases at room temperature. The ground-state geometry, HOMO/LUMO energies, vertical transition energies and the corresponding oscillator strengths have been calculated for the isolated molecules. The redox behavior of octaalkoxycarbonyl phthalocyanines was investigated by cyclic voltammetry and their aggregation in solution by 1H NMR spectroscopy. The supramolecular structure of the liquid crystalline mesophase of a novel phthalocyanine bearing branched alkyl chains was studied by powder X-ray diffraction. The length and branching of peripheral alkyl chains are found to be two structural parameters affecting the formation of mesophases and self-aggregation in solution. © The Royal Society of Chemistry.