Boronic ester-substituted terpyridine metal complex as a novel fluoride-sensitive redox receptor

The boronic ester-disubstituted terpyridine 1 Fe(II) complex [Fe(II)1(2)](2+) has been used as a redox-active receptor for fluoride. Upon binding of F- to the boronic ester moieties, the Fe(II)/Fe(III) oxidation peak of this metal complex is shifted toward less positive potentials. The magnitude of the shift (around 160 mV) is much larger than that measured with Cl- (20 mV) whereas other anionic species (i.e. Br-, NO3- and SO42-) do not interact. Such a variation is consistent with a more than 500-fold increase of the F--binding constant upon the oxidation of Fe(II) to Fe(III). Further UV-Vis spectroscopy data would indicate the formation of two complexes of stoichiometries 1:1 and 1:2 (receptor:fluoride), successively. (C) 2001 Elsevier Science Ltd. All rights reserved.