Synthesis and Hollow-Sphere Nanostructures of Optically Active Metal-Free Phthalocyanine

Optically active metal-free phthalocyanine (1) decorated with four octyl chains linked through binaphthyl units to the phthalocyanine ring was designed and prepared. This compound was characterized by a wide range of spectroscopic methods in addition to elemental analysis. By employing a solution injection method, both the (R) and (S) enantiomers self-assemble into nanoparticles. Surprisingly, with the addition of a small amount of cetyltrimethylammonium bromide (CTAB), nanostructures with hollow-sphere morphologies were formed. The hollow-spherical structure was determined by transmission electronic microscopy and scanning electronic microscopy. X-ray photoelectron spectroscopy together with FTIR spectra indicates the supramolecular structures formed from the metal-free phthalocyanine molecules. Low-angle X-ray diffraction reveals the stacked phthalocyanine molecules with a face-to-face configuration in the nanoscale hollow spheres formed with the help of CTAB surfactant. The formation of H-aggregates in the nanoscale hollow spheres is further confirmed by electronic absorption spectroscopic result. This work, representing the first example of controllable organic nanostructures with a hollow sphere morphology fabricated from phthalocyanine provides an effective method towards phthalocyanine hollow nanospheres. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)