Controlled Helical Organization in Supramolecular Polymers of Pseudo‐Macrocyclic Tetrakisporphyrins

Tetrakisporphyrin monomers with amino acid side chains at each end form intramolecular antiparallel hydrogen‐bonds to adopt chirally twisted pseudo‐macrocyclic structures that result in right‐handed and left‐handed (P)‐ and (M)‐conformations. The pseudo‐macrocyclic tetrakisporphyrin monomers self‐assembled to form supramolecular helical pseudo‐polycatenane polymers via head‐to‐head complementary dimerization of the bisporphyrin cleft units in an isodesmic manner. The formation of one‐handed supramolecular helical pseudo‐polycatenane polymers was confirmed by circular dichroism spectroscopy. The methyl and iso‐propyl groups at the stereogenic center greatly enhanced the induced circular dichroism (CD) in the Soret bands of the supramolecular helical pseudo‐polycatenane polymers. The induced CDs were reduced upon the introduction of large iso‐butyl and tert‐butyl groups. Atomic force microscopy revealed well‐grown and long supramolecular helical pseudo‐polycatenane polymer chains with chain lengths in the range of 361 to 13.6 nm. The right‐handed helical chains were established by the self‐assembly of the right‐handed (P)‐conformation of the pseudo‐macrocyclic monomer.