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Free keywords:
Experimental charge density; Interhalogen contacts; Halogen bonds; Hydrogen bonds; Secondary interactions
Abstract:
Remarkably short contacts involving halogen atoms, although well documented decades ago, have recently found increasing interest as potentially relevant in the context of crystal engineering. X-ray diffraction data of sufficient quality and resolution allow to experimentally determine the charge density in crystals featuring such contacts and hence to associate this observable quantity with effects of molecular packing. Results from charge density studies covering interhalogen contacts over a distance range significantly shorter and considerably longer than mere van-der-Waals contacts are reported, and their relevance for the crystal chemistry of the compounds under investigation is discussed. A first trend for intra- and intermolecular Cl···Cl interactions indicates that the shortest among these contacts, with a distance of ca. 3.2 Å, can compete with weak hydrogen bonds.
