Selectivity tune of fluoride ion sensing for phenolic OH-containing BODIPY dyes

A series of BODIPY dyes bearing phenolic OH in the meso-phenyl moiety were designed and synthesized for colorimetric and fluorescent detection of F− ions by way of O–H⋯F hydrogen bonding interactions. Both the electron-donating group attached on the meso-phenyl skeleton, such as methoxy group and t-butyl group, and the substituting position of the phenolic OH have dramatic influences on the chemical shift of OH, pKa of OH, and the binding constant of OH to F−. The binding selectivity to F− over other anions may be greatly improved by down-regulating the binding constant to F− through structure optimization. As a result, BODIPY 7 can selectively probe F− in both absorption and fluorescence modes in acetonitrile and does not response to other anions including AcO−. The observed structure dependence of the binding selectivity may provide guidelines for the development of new F− colorimetric or fluorescent sensors of high selectivity.