Synthesis of helicenediamine oligomers and their formation of multilayer structures in aqueous solvents

Optically active polyamine oligomers containing three to six (P)-5,8-bis(aminomethyl)-1,12-dimethylbenzo[c]phenanthrenes were synthesized employing the two-directional chain extension method. It was critical for the effective coupling of amines and aldehydes to precipitate imine intermediates using the appropriate solvents. UV, CD, fluorescent, and NMR spectroscopic studies revealed that the above-mentioned oligomers form multilayer structures in aqueous solvents, while they form random coil structures in methanol. Such layer structures contained helicene dyads with an anti-conformation in which the BC-rings of helicenes were stacked on each other, and 1, 1 2-dimethyl groups were arranged in the opposite direction. A diastereomeric trimer was also synthesized, the layer structure of which was different from that of the parent trimer. The stereochemistry of the helicene moiety influenced the layer structure.