Selenacalix[3]triazines: Anion Versus Proton Association

Selenacalix[3]triazines, cyclotrimeric metacyclophanes with direct Se linkages between the heteroaryl constituents, were shown to associate with various guest species. The preorganization of three electron deficient triazine rings allows for anions to bind through anion- interactions, and alignment of the central nitrogen lone pairs and the well-defined size of the macroring enable association with a single proton. Extended UV/Vis titration studies indicated a clear difference in complexation behavior depending on the outer-rim substitution pattern. The hostguest properties of analogous selena- and thiacalix[3]triazines were found to be notably different.