Halide Ions Complex and Deprotonate Dipicolinamides and Isophthalamides: Assessment by Mass Spectrometry and UV-Visible Spectroscopy

The F-, Cl-, and Br- binding selectivity of bis(p-nitroanilide)s of dipicolinic and isophthalic acids was studied by using competitive electrospray mass spectrometry and UV-Visible spectroscopy. Both hosts prefer binding Cl- over either F- or Br-. Host deprotonation was observed to some extent in all experiments in which the host was exposed to halide ions. When F- was present, host deprotonation was often the major process, whereas little deprotonation was observed by Cl- or Br-, which preferred complexation. A solution of either host changed color when mixed with a F-, H2PO4-, di- or triphenylacetate solution.