TRIPTYCENE- AND BIPHENYLENE-BASED BIFUNCTIONAL LEWIS ACIDS AS ANION RECEPTORS
Abstract
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.
Citation
Chen, Chang-Hong (2018). TRIPTYCENE- AND BIPHENYLENE-BASED BIFUNCTIONAL LEWIS ACIDS AS ANION RECEPTORS. Doctoral dissertation, Texas A & M University. Available electronically from https : / /hdl .handle .net /1969 .1 /174117.