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 1 H 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.

Blends of two metal-free phthalocyanine mesogens exhibiting different mesophases (Col r phase from room temperature to isotropization for the first one, and Col r at room temperature then Col h from around 60 °C to isotropization for the second one) have been studied in order to determine the relationship between the type of mesophase and the alignment behavior. The phase diagram of this system has been built and evidence of full solid-state miscibility of the two pure constituents in all proportions and temperatures is presented. Investigation of phase alternation at room temperature as a function of composition revealed that border compositions exhibit Col r phases similar to the pure constituents, whereas Col h mesophase was stabilized for intermediate compositions. Combined polarized optical microscopy observations and X-ray diffraction measurements showed that homeotropic alignment is adopted only for mixed samples exhibiting Col h mesophase, thus demonstrating that the presence of a Col h mesophase is a necessary condition for homeotropic alignment.

SummaryA series of phthalocyanine-C60 dyads 2a–d was synthesized. Key steps in their synthesis are preparation of the low symmetry phthalocyanine intermediate by the statistical condensation of two phthalonitriles, and the final esterification of the fullerene derivative bearing a free COOH group. Structural characterization of the molecules in solution was performed by NMR spectroscopy, UV–vis spectroscopy and cyclic voltammetry. Preliminary studies suggest formation of liquid crystalline (LC) mesophases for some of the prepared dyads. To the best of our knowledge, this is the first example of LC phthalocyanine-C60 dyads.

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