Fluoride sensing by polymeric membranes based on organoboron Lewis acid receptors

摘要

Intensive research is focused on organoboron receptors characterized by strong and selective interactions of three-coordinate boron center ("hard" Lewis acid) with fluoride ions ("hard" Lewis base). In this work, newly syntesized 4-octyloxyphenylboronic acid (OPBA) and pinacol ester of 2,4,6-trifluorophenylboronic acid (PE-PBA) were proposed as fluoride-selective ionophores in polymer membranes. The membranes containing OPBA showed enhanced selectivity, but the slopes of the fluoride responses in acidic conditions were super-Nernstian. In contrary, theoretical behavior was noticed in the case of membranes doped with the pinacol ester derivative. A response mechanism of the polymer membrane electrodes based on organoboron receptors was proposed on the basis of potentiometric and 19F NMR studies.