Discotic liquid crystals of transition metal complexes. Part 24 Synthesis and mesomorphism of porphyrin derivatives substituted with two or four bulky groups

Abstract

We have synthesized nine novel porphyrin derivatives, 1-8 and 1-Cu, substituted with various steric hindrance groups and long flexible chains in order to investigate the relationship between the molecular type of porphyrin derivatives and the resulting mesophase. Type 4 disc-like (C ₁₂ O) ₁₆ -TTPH ₂ (1) and (C ₁₂ O) ₁₆ -TTPCu (1-Cu) derivatives exhibit D _h columnar mesophases, which are the first examples of meso-substituted porphyrin metal-free derivatives and copper complexes. Type 5 strip-like (C _n O) ₈ -BTPH ₂ [4 (n=12), 5 (n=16)] derivatives having eight long chains at the 5,15-positions exhibit D _rd columnar mesophases. On the other hand, the type 5 (C ₁₂ O) ₄ -BTPH ₂ (6) derivative having four long chains exhibits discotic lamellar D _L.rec1 and D _L.rec2 mesophases which have a two-dimensional rectangular structure within the layer. The (C ₁₂ O) ₄ -BPPH ₂ (7) type 6 derivative also shows a D _L lamellar mesophase. Bruce et al. reported that type 3 rod-like porphyrin derivatives show calamitic mesophases of S _B , S _E and S _E′ phases. We revealed from these types of mesogenic porphyrin derivatives that such a successive change of the molecular structures causes their mesophases to change from discotic columnar to discotic lamellar, and further to calamitic.