Noncovalent Interactions of π Systems with Sulfur - The Atomic Chameleon of Molecular Recognition.

The relative strength of noncovalent interactions between a thioether sulfur atom and various pi systems in designed top pan molecular balances was determined by NMR spectroscopy. Compared to its oxygen counterpart, the sulfur atom displays a remarkable ability to interact with almost equal facility over the entire range of pi systems studied, with the simple alkene emerging as the most powerful partner. With the exception of the O center dot center dot center dot heteroarene interaction, all noncovalent interactions of sulfur with pi systems are favoured over oxygen.