Discotic liquid crystals of transition metal complexes 47: synthesis of phthalocyanine-fullerene dyads showing spontaneous homeotropic alignment

Abstract

In previous work, we successfully synthesized the first columnar liquid crystalline 1:1 phthalocyanine(Pc)-fullerene( C60 ) dyad, C12(OMalC60)PcCu (4), showing spontaneous homeotropic alignment, by using Bingel reaction. However, it gave undesirable 2:1 and 3:1 Pc- C60 by-products at the same time, so that the 1:1 Pc- C60 dyad (4) could be obtained in a very low yield (20%). On the other hand, in this work we have prepared novel Pc- C60 dyads, C12(OFbaC60)PcM (8: M = Co (a), Ni (b) and Cu (c)), by using Prato reaction. Very interestingly, it gave almost only the target 1:1 Pc- C60 dyads 8a–8c in very high yields (81–96%) with negligible amount of Pc- C60 by-products. These dyads 8a–8c and the precursor Pc derivatives were characterized by polarizing microscope, differential scanning calorimeter and temperature-dependent X-ray diffractometer. Thus, it was revealed that each of the dyads and precursors shows spontaneous homeotropic alignment in their Coltet mesophase.