Modifying the proton transfer of 3,5-bis(2-hydroxyphenyl)-1H-1,2,4-triazole by water, confinement and confined water

[Display omitted] •Proton transfer of 3,5-bis(2-hydroxyphenyl)-1H-1,2,4-triazole(bis-HPTA) was studied.•Proton triggered proton transfer is more favored in water than in organic solvents.•Intermolecular proton transfer takes place in anionic form of bis-HPTA in water.•In β-cyclodextrin, intermolecular proton transfer is prevented in bis-HPTA anion.•The confined water breaks the intramolecular hydrogen bond in bis-HPTA. The effect of water, confinement and confined water on the proton transfer of 3,5-bis(2-hydroxyphenyl)-1H-1,2,4-triazole (bis-HPTA) was investigated. Water alters the proton transfer process. At higher pH, an anion is formed in water and it undergoes intermolecular proton transfer and forms a keto tautomer. Confinement of molecule in β-cyclodextrin affects the intramolecular proton transfer. It also prevents the intermolecular proton transfer of the anionic form. In reverse micelle, the molecule resides in the interfacial region and interacts with bound water. The intermolecular hydrogen bond of the surfactants opens the intramolecular hydrogen bond in the weaker β-ring of bis-HPTA. It led to single tautomer emission from bis-HPTA. An increase in water amount enhances the relative amount of trans-enol, but predominantly tautomer emission is observed.