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Fluoride ion sensing by an anion-π interaction
1Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, Florida 32306, United States.
Abstract:
We report the discovery of a supramolecular interaction (anion-π and charge/electron transfer, CT/ET) involving fluoride ion and π-electron deficient colorless naphthalene diimide (NDI) receptors. Strong electronic interactions between lone-pair electrons of F(-) ion and π*-orbitals of the NDI unit lead to an unprecedented F(-)→NDI ET event, which produces an orange colored NDI(•-) radical anion. Further reduction of NDI(•-) by another F(-) ion produces a pink colored NDI(2-) dianion, rendering NDI a colorimetric F(-) sensor. Preorganization of two NDI units in overlapping positions using folded linkers improves their selectivity and sensitivity for the F(-) ion significantly, allowing F(-) detection at nM concentration in 85:15 DMSO/H(2)O solutions.
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