Translation of helical chirality from polymer into monomer: supramolecular polymerization of a chirality-memory molecule with an asymmetric Pd(II) complex

A chirality-memorizing saddle-shaped porphyrin (12H) with 3,5-dipyridylphenyl side arms at the opposite meso positions underwent supramolecular polymerization in CH2Cl2 with a chiral Pd(II) complex of 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (PdII(BINAP)), forming a ladder-shaped polymer (32H) with a prevailing one-handed helical chirality. When this polymer was poured into AcOH containing 1,3-bis(diphenylphosphino)propane (DPPP) as a decomplexing agent, 32H was depolymerized in a stereochemically retentive way to give optically active 12H, hydrogen-bonded with AcOH. Although a cyclodimeric reference of 32H, formed from 22H having two 3-pyridylphenyl meso substituents in conjunction with PdII(BINAP), behaved similar to 32H, the translation efficiency of helical chirality was lower than that in the case with 32H.