TRIPTYCENE- AND BIPHENYLENE-BASED BIFUNCTIONAL LEWIS ACIDS AS ANION RECEPTORS
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The chemistry of main group-based polydentate Lewis acids has drawn considerable attention over the past few decades, owing to application in anion sensing, anion transport, small molecule activation and catalysis. Bidentate Lewis acids featuring the rigid 1,8-naphthalenediyl or ortho-phenylene backbones are the most studied examples of such systems. Owing to the short spacing of the two Lewis acidic sites, these derivatives can only chelate monoatomic anions or polyatomic anions amenable to μ(1,1) ligation. Bearing in mind that this limitation could be overcome through modification of the backbone architecture, we have recently become interested in bidentate Lewis acids with an increased separation between the Lewis acidic centers. It occurred to us that triptycene and biphenylene backbones may offer extended separation between Lewis acidic centers, which may facilitate the selective complexation of larger anions. In this thesis, we report on the chemistry of triptycene- and biphenylene-based diboranes as large-bite bidentate Lewis acids for the μ(1,2) complexation of the cyanide anion as well as hydrazine. The results demonstrate that the biphenylene platform can be used as a support for hybrid ditopic Lewis acids containing both borane and borinic acid moieties. An investigation of this unusual bifunctional Lewis acid reveals that this is well for the complexation of the fluoride anion in aqueous media. Finally, this thesis shows that these platforms can also be incorporated in antimony-based bifunctional derivatives. The most interesting results have been obtained with a triptycene-based distiborane which shows a remarkable affinity for fluoride anions. Altogether, these results indicate that changes in the nature of the backbone have a defining influence on the binding selectivity of bidentate Lewis acids. These results may also define new directions in the chemistry of these main group compounds with applications in molecular recognition, sensing as well as in the mitigation of toxic chemicals.
Chen, Chang-Hong (2018). TRIPTYCENE- AND BIPHENYLENE-BASED BIFUNCTIONAL LEWIS ACIDS AS ANION RECEPTORS. Doctoral dissertation, Texas A & M University. Available electronically from