Merging antimicrobial and visible emission properties within 1,3,4-trisubstituted-1,2,3-triazolium salts

Bioactive molecules displaying visible wavelength emission can be useful for bioimaging, chemosensing and photodynamic therapy applications. Reported herein are 1,3,4-trisubsituted-1,2,3-triazolium salts displaying both antimicrobial and visible emission properties. Using a click chemistry approach, 2-fluorenyl, 1-naphthyl, 2-naphthyl, 2-anthracenyl and 1-pyrenyl units were incorporated at the N1 position, imparting visible emission properties to their triazolium bromide salts with Stokes shifts greater than 100 nm relative to the emission of their triazole precursors. The increasing size of such hydrophobic aryl units impacts minimum inhibitory concentration (MIC) values against Gram-positive bacteria, Gram-negative bacteria and yeast, and can be counterbalanced by hydrophobic substituent variation at other positions of the molecule in order to preserve bioactivity. Among the series of compounds studied are analogs displaying blue, green and yellow colored emission and MIC values as low as 0.4 μM (Gram-positive bacteria), 8 μM (Gram-negative bacteria) and 2 μM (yeast). XRD analysis validates the regioselective benzylation at the N3 position of the 1,2,3-triazole ring and the ability of such compounds to associate through dimeric intermolecular π-stacking interactions. [Figure not available: see fulltext.]