Simultaneous σ‐hole and hydrogen bonding by sulfur‐ and selenium‐containing heterocycles

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Abstract
When a Group V, VI, or VII atom forms a covalent bond, its bonding orbital has a deficiency of electronic charge in its outer (noninvolved) lobe. This is called a σ‐hole. If the atom is sufficiently polarizable, the σ‐hole may have a positive electrostatic potential which can interact with a nucleophilic site in its proximity to form a noncovalent bond. In this article, we show computationally, for a series of sulfur and selenium heterocycles, how the two σ‐holes on each S or Se atom are affected by changes in the molecular framework and substituents. It is possible to selectively design σ‐holes of appropriate strength and orientation for specific purposes, e.g. drug‐receptor interactions or crystal engineering. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008