Supramolecular Helical Polymer Formed Via Complementary Dimerization of Bisporphyrin Cleft

Abstract

We have been developing supramolecular polymers directed by unique host-guest motifs.1,2 During study, a tetrakisporphyrin monomer was discovered to form the supramolecular helical polymers.3,4 A lack of chirality resulted in the racemic mixture of the supramolecular helical polymers. In this presentation, we report that the chirally-twisted pseudo macrocyclic tetrakisporphyrin monomer is self-assembled to form the one-handed helical supramolecular structures. Two amino acid side chains were installed at the termini of a tetrakisporphyrin monomer. The intramolecular antiparallel hydrogen bonding between the amino acid side chains resulted in the pseudo macrocyclic conformation, which was chirally-twisted. The right-handed and left-handed conformations of the pseudo macrocyclic monomer are determined by the absolute configuration of the stereogenic centers. The chirally-twisted pseudo macrocyclic monomer was self-assembled to result in the one-handed helical structures with very high association constants. The well-developed supramolecular chains generated entangled polymer solution, which suggests the formation of the well-developed long supramolecular polymer chains. Atomic force microscopy visualized the long supramolecular polymer chains with the length more than 100 nm. The right-handed helical morphology was formed from the D-amino acid side chains.