Liquid Crystals of Phthalocyanine-Fullerene Dyads Exhibiting Homeotropic Alignment and Spiranthes-like Supramolecular Structure Useful for Solar Cells

A homologous series of the phthalocyanine-fullerene dyads, (CnS)6PcCu-Cm-C60 (4a~g) [(n, m) = (14, 8) (a); (14, 10) (b); (14, 12) (c); (16, 8) (d); (16, 10) (e); (16, 12) (f); (18, 10) (g)], have been synthesized with changing both the chain length of the peripheral alkylthio group (n) and the spacer length (m) between Pc and C60 in order to find out the homologues showing perfect homeotropic alignment at rt. As a result, each of the dyads 4a~g shows perfect homeotropic alignment in their hexagonal ordered columnar (Colho) mesophases and the homologues 4a~c having shorter alylthio chains (n = 14) show perfect homeotropic alignment at rt. Very interestingly, the spherical C60 parts form a helical structure around the column formed by the disk-like Pc parts. This supramolecular structure very resembles spiranthes flower. The spiranthes-like supramolecular structure is compatible with one-dimensional nano-array expecting the high conversion efficiency of solar cells.