Axially chiral amino acid scaffolds as efficient fluorescent discriminators of methanol-ethanol

We report a unique fluorescence sensor based on an axially chiral unnatural triazolyl aromatic amino acid scaffold ((Ar)TAA) for discrimination of methanol from ethanol via a switch on fluorescence response. All three sensors, the simple scaffold ((Ar)TAA), and the mono-(PyAm-(Ar)TAA) and bis-pyrenyl-(Py2Am-(Ar)TAA) amides, show similar sensitivity and detection limit ranging from 0.5-2.1 v/v% of ethanol. The solid films of these sensors are also found to be effective in sensing ethanol vapour via generation of a distinct and enhanced fluorescence signal. All our experimental results suggest the role of axial chirality of the hairpin-shaped scaffold in differential solvation guided H-bonding interaction and discriminating between ethanol and methanol with a switch-on fluorescence response.