Boronic acid based photoinduced electron transfer (PET) fluorescence sensors for saccharides

A simple three step synthesis was developed to provide six novel modular sensors, consisting of three para sensors, and three meta sensors with naphthalene, anthracene and pyrene fluorophores. The interaction of the six sensors with the saccharides: D-glucose, D-fructose, D-galactose, and D-mannose, were evaluated. All sensors displayed increasing fluorescence intensity upon the addition of these saccharides, with all of the sensors showing enhanced selectivity for D-glucose over D-galactose, D-fructose and D-mannose. High affinity (K-obs) was also observed for the meta sensors with respect to the para sensors. The naphthalene and anthracene meta sensors showed particularly high affinity (K-obs) for D-galactose. Circular dichroism spectroscopy was used to probe the structures of the complexes formed. Cyclic complexes were formed between all six sensors and D-glucose. Whilst naphthalene and anthracene meta sensors which displayed high affinity for D-galactose also formed cyclic complexes with that saccharide.