The main goal of our research activities is to develop applications of halogen bonding in organocatalysis. To this end, we prepared neutral polyfluorinated and polyiodinated multidentate halogen bond donors which are based on terphenyl and quaterphenyl backbones and used them as catalysts in a benchmark reaction. Since this reaction is based on halide abstraction, we investigated in more detail the binding of the halogen bond donors to halides and compared the adduct formation in all three phases: gas-phase, solution, and solid state.<br/><br/>The highly symmetric Lewis acidic axis of these organocatalysts also make them ideally suited for molecular recognition processes. In a first proof-of-principle case, molecular recognition between the quaterphenyl-based polyfluorinated halogen bond donor and an orthoamide was realized. The latter featured Lewis basic binding sites which are perfectly positioned to form three virtually identical halogen bonds with the Lewis acid. This complex thus represents the first case of well-defined three-point halogen bonding. The binding to this ideal counterpart is orders of magnitude stronger than the unselective binding to other amine reference compounds.<br/><br/>In an extension of this work, the same halogen bond donor was also used in microquartz balance studies in the gas phase. Acetone was selectively detected, even in the presence of water.

Multidentate halogen bonding organocatalysts in molecular recognition studies

253rd National Meeting (2017)

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