Helical self-assembly of optically active phthalocyanine derivatives in mesophase. Effect of the position of chiral substituents on the handedness and mesophase textures

Abstract

Two phthalocyanine derivatives with peripheral chiral (S)-2-methylbutanol moieties on the α- or β-position of the phthalocyanine ring, namely {(1,8,15,22-tetra[(S)-2-methylbutoxy]} phthalocyaninato copper complex (S)-CuPc(α-OC5H11)4 (1) and {(2,3,9,10,16,17,23,24-octa[(S)-2-methylbutoxy]} phthalocyaninato copper complex (S)-CuPc(β-OC5H11)8 (2) were synthesized. Their helical self-assembly behavior in mesophase were comparatively investigated by electronic absorption and circular dichroism spectroscopy, differential scanning calorimeter, polarized optical microscope and X-ray diffraction technique. In mesophase, (S)-CuPc(α-OC5H11)4 (1) self-assembled into rectangular columnar liquid crystals with left-handed fan texture. However, hexagonal columnar liquid crystals with well-ordered, rare, right-handed spherulites were formed from (S)-CuPc(β-OC5H11)8 (2). These results clearly indicated the effect of the position of chiral substituents on the handedness and mesophase textures of self-assembled liquid crystals and will be helpful towards rational design and preparation of chiral liquid crystal materials.