Clathrate formation and molecular recognition by novel chalcogen-cyano interactions in tetracyanoquinodimethanes fused with thiadiazole and selenadiazole rings

Article abstract of DOI:10.1021/ja00034a041

The intermolecular contacts between chalcogen atoms and cyano lone pairs were found to stabilize the crystalline state by electrostatic interaction. This interaction is one of the sources of the directionality in crystal packing of organic molecules and causes the formation of various types of inclusion lattices in the charge-transfer (CT) crystals of 1-3. By using highly selective formation of CT crystals with substituted aromatic hydrocarbons, particular isomers such as p-xylene or 2,6-dimethylnaphthalene (2,6-DMN) could be separated from the corresponding isomer mixtures. Lattice-related interaction plays a more significant role than molecular orbital interaction in the observed selectivity for para-disubstituted benzenes. However, the latter interaction is important for the recognition of 2,6-DMN from the 2,7 isomer.