Aromatic Foldamers with Iminodicarbonyl Linkers: Their Structures and Optical Properties

Carboxamides possessing naphthalene rings connected by multiple iminodicarbonyl linkers were
synthesized. These molecules forced the naphthalene rings to be placed in the positions facing
each other, and they form helical foldamers both in solution and in the crystalline state. Their
folding structures were investigated by single-crystal X-ray analysis and 1H NMR spectroscopy.
Their absorption and fluorescence spectra showed a red shift as the number of naphthalene moieties
increased. This remarkable change is based on the intramolecular interaction between naphthalene
moieties. Helicity of the foldamer can be controlled by the introduction of chiral auxiliaries at imide
nitrogen atoms, which results in an observation of induced circular dichroism.