A homologous series of the phthalocyanine-fullerene dyads, Cn-PcM(OFbaC60) (n = 6, 8, 10, 12; M = Cu , Ni , Co : 3a–3f) have been synthesized to obtain homeotropic alignment at rt and investigate the effects of spacer chain length (n = 6, 8, 10, 12) and central metal ( M = Cu , Ni , Co ) on the mesomorphism. Interestingly, the shorter-spacer-substituted (n = 6, 8; M = Cu ) dyads 3a and 3b showed a hexagonal columnar mesophase (Colh), whereas the longer-spacer-substituted (n = 10, 12; M = Cu , Ni , Co ) dyads 3c–3f showed a tetragonal columnar mesophase (Coltet). Moreover, each of the homologs 3a–3e shows perfect homeotropic alignment in both the Colh and Coltet mesophases at rt. More interestingly, these columnar mesophases gave a very unique XRD reflection peak denoted as Peak H in a very small angle region of 0.8 < 2θ < 2.0 degree. We have established at the first time from our developed two new XRD sample preparation techniques that the Peak H is due to the helical structure of fullerenes around columns formed by one-dimensionally stacked Pc cores. 1D nano array structure of donor and acceptor between two electrodes is recently proposed to obtain higher photoelectric conversion efficiency for organic thin film solar cells. This 1D nano array structure is almost compatible with the present homeotropically aligned Pc- C 60 dyads 3a–3f between two glass plates. Hence, these novel Pc- C 60 dyads 3a–3f may be very suitable to organic thin film solar cells.
We have synthesized novel hexaphenoxy-substituted phthalocyanine derivatives, 2-(12-hydroxydodecyloxy)-3-methoxy-9,10,16,17,23,24-hexakis(3,4-di-n-alkoxyphenoxy)phthalocyaninato copper(II) (abbreviated as Cn(OC12OH)PcCu : n = 10, 12, 14), and investigated their columnar mesomorphism and homeotropic alignment property. These hexaphenoxy-substituted Pc derivatives could be successfully isolated and purified from the mixture products by polarity difference. It was revealed by using polarizing optical microscopic observations, differential scanning calorimetry and temperature-dependent X-ray diffraction studies that each of the hexaphenoxy-substituted Pc derivatives has plural mesophases, and that the tetragonal columnar (Coltet) mesophase shows spontaneous perfect homeotropic alignment between two non-surface-treated glass plates without any defects and polydomain boundaries.