A highly selective ratiometric bifunctional fluorescence probe for Hg²⁺ and F⁻ ions

A triarylborane derivative BN-S, which contains a Hg²⁺-responsive dithioacetal group and a F⁻-responsive boryl group, has been designed and synthesized via the functionalization of 2-dimesitylboryl-2′-(N,N-dimethylamino)biphenyl core skeleton with a dithioacetal substituent. This compound displays intense intramolecular charge transfer fluorescence, even for its nano-aggregates in water. The Hg²⁺-promoted deprotection of the dithioacetal group and complexation of F⁻ with the tri-coordinate boron center cause hypochromism of fluorescence to different extents. And thus BN-S behaves as a promising ratiometric bifunctional fluorescence probe to detect Hg²⁺ and F⁻ simultaneously. In addition, the detection of Hg²⁺ is performable in aqueous medium using its nano-aggregates.