Homochiral Double Helicates Based on Cyclooctatetrathiophene: Chiral Self-Sorting with the Intramolecular S⋅⋅⋅N Interaction.

The design and synthesis of homochiral double helicates are reported that are constructed by means of Ag-induced supramolecular self-sorting of saddle-shaped cyclooctatetrathiophene-based pyridine ligands (1 and 2). The intramolecular S⋅⋅⋅N interaction ensures that the thiophene and pyridine rings of ligands 1 and 2 are in coplanar and syn-locked structures. In the presence of Ag+ , the racemic ligands 1 and 2 only afforded homochiral double helicates, indicating effective chiral self-sorting process under the influence of the S⋅⋅⋅N interaction. The X-ray crystal structure of 12 Ag2 reveals a pair of homochiral double helicates (R,R,R,R)-12 Ag2 and (S,S,S,S)-12 Ag2 . Furthermore, chiral resolution of racemic ligand 1 was achieved by chiral-phase HPLC, and the enantiomers and their corresponding enantiopure Ag complexes were characterized.