2.B.58. The Phosphonium Borane Anion Transporter (PBAT) Family
In order to synthesize selective transmembrane anion transporters, a series of phosphonium boranes of general formula [p-RPh2 P(C6 H4 )BMes2 ]+ were synthesized and evaluated (Park and Gabbaï 2020). Variation of the R group appended to the phosphorus atom determines the lipophilicity of these compounds, their Lewis acidity, and their transport activities. Anion transport experiments in POPC-based large unilamellar vesicles showed that these main-group cations are highly selective for fluoride anions, which are transported more than 20 times faster than the chloride anion. Finally, this work shows that the anion transport properties of these compounds are extremely sensitive to steric crowding about the boron atom, pointing to the crucial involvement of the Group 13 element as the anion binding site (Park and Gabbaï 2020).