Hydrosulfide (HS−) Recognition and Sensing in Water by Halogen Bonding Hosts

Hydrogen sulfide (H2S) plays a crucial signalling role in a variety of physiological systems, existing as the hydrosulfide anion (HS−) at physiological pH. Combining the potency of halogen bonding (XB) for anion recognition in water with coumarin fluorophore incorporation in acyclic host structural design, the first XB receptors to bind and, more importantly, sense the hydrosulfide anion in pure water in a reversible chemosensing fashion are demonstrated. The XB receptors exhibit characteristic selective quenching of fluorescence upon binding to HS−. Computational DFT and molecular dynamics simulations in water corroborate the experimental anion binding observations, revealing the mode and nature of HS− recognition by the XB receptors. Reversible chemosensing of hydrosulfide (HS−) in pure water is demonstrated using halogen bonding (XB) fluorescent hosts. The XB receptors exhibit characteristic selective quenching of fluorescence upon binding HS− whereas the hydrogen bonding receptor analogues proved incapable of functioning as chemosensors under aqueous conditions.