Self-organization of hydrogen-bonded optically active phthalocyanine dimers

Zinc(II) phthalocyanines 4 and 5 decorated with six optically active alkyl chains and one chial diol were synthesized from two phthalonitriles using mixed tetramerization reactions. Self-organizing properties of these complexes and related compounds 3, 6, and 7 in CHCl₃ solution and thin film were studies by UV-vis, Fourier transform infrared (FT-IR), circular dichroism (CD), vapor pressure osmometeric, and powder X-ray diffraction (XRD) measurements. Zinc phthalocyanines having a chiral diol formed an optically active dimer in CHCl₃ solution through the formation of an intermolecular hydrogen bond between two diol groups. Differential scanning calorimetry, temperature-controlled FT-IR, UV-vis, XRD, and CD measurements for thin films indicated that 4 and 5 organized into two different structures, depending on the temperature. At room temperature, the polymeric hydrogen bond among the diol groups allowed the construction of a lamellar sheet. However, the cleavage of a hydrogen-bond network above 130°C caused the structure to change to a hexagonal columnar phase, in which zinc phthalocyanine molecules are arranged in a left-handed helix.