Defined halogen bond receptors for polymeric architectures: Adaption of behavior in solution as tool to create new functional materials

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The design of selective anion binding sites, which enable a detection, binding and transport of relevant anions, is one of the most important fields in supramolecular chemistry. While anion detection based on hydrogen bonds is well established, the potential of halogen bonds for selective anion recognition was only realized very recently. In contrast to the hydrogen bond, the strongly related halogen bond exhibits a stronger orientational preference, a higher covalent contribution to the binding as well as a stronger interaction with a Lewis-basic partner, which enables the construction of highly selective anion binding sites.Halo-1,2,3-triazoles and halo-1,2,3-triazoliums feature highly Lewis-acidic halogen atoms that are capable of establishing strong halogen bonds. Owing to the facile and modular synthesis of these heterocycles, the halogen bond can be readily implemented into a variety of different systems. The research described in this proposal aims at exploiting the great potential of halogen bonds by making use of the facile and modular synthesis of halo-1,2,3-triazoles and halo-1,2,3-triazoliums. In more detail, the following sub-projects (1 to 5) will be investigated: 1) By the help of specific modifications on the anion binding site, the effect of different parameters, namely the bite angle to the anion, the spacer between the halogen-bond donors the electron-withdrawing group as well as the preorganization of the system, will be studied.2) By combining a ruthenium(II) complex with an anion binding side, selective anion sensors with low detection limits will be constructed.3) By exploiting cooperative effects, ion-pair receptors that exhibit high selectivity and binding strength for different ion pairs will be designed. 4) The higher directionality as well as the higher anion affinities of halogen bonds relative to analogous hydrogen-bond-based systems is expected to enable the design of highly efficient organo-catalysts. The modular synthesis of halo-1,2,3-triazoles allows a simple integration of chiral moieties, which, in turn, allows the construction of highly interesting catalysts for enantioselective reactions. 5) Since halogen bonds are strong but labile, the potential application in self-healing materials is planned.The application of the halogen bond for anion recognition is currently a hot topic and offers an immense potential. This research described herein aims at developing new halogen bond donors in order to design new anion sensors, organo-catalysts as well as functional materials.