2.B.59. The Strapped CalixPyrrole (SC4P) Family
Fluoride can be a substrate of synthetic anion transporters (see TC Families 2.B.57, 2.B.58 and this family). Clarke et al. 2016 reported the direct measurement of fluoride transport across lipid bilayers facilitated by a series of strapped calixpyrroles and showed that these compounds facilitate transport via an electrogenic mechanism (determined using valinomycin and monensin coupled transport assays and an additional osmotic response assay). An HPTS transport assay was used to quantify this electrogenic process and assess the interference of naturally occurring fatty acids with the transport process and Cl- over H+/OH- transport selectivity (Clarke et al. 2016).
A calixpyrrole with a bisurea strap that functions as a receptor and transporter for H2PO4-, relying on the formation of eight hydrogen bonds and efficient encapsulation of the anion has been described (Cataldo et al. 2023). Using a phosphate-sensitive lanthanide probe and 31P NMR spectroscopy, they demonstrated that this receptor can transport phosphate into vesicles by H2PO4-/Cl- antiport, H2PO4- uniport, and Cs+/H2PO4-/ symport mechanisms.