Theoretical DFT and matrix isolation FTIR studies of 2-(1,2,4-triazolyl)phenol isomers

Highlights: • Three isomers of 2-(1,2,4-triazolyl)phenol (TRP) are isolated in Ar and N₂ matrices. • The most stable TRP isomers are stabilized by the intramolecular OH⋯N hydrogen bond. • The structure, isomerization pathways and vibrational spectra of TRP are presented. The structure, isomerization pathways and vibrational spectra of the important heterocyclic 2-(1,2,4-triazolyl)phenol molecule were investigated by DFT calculations and matrix isolation FTIR spectroscopy. Among forty-five minima located on PES three isomers with intramolecular hydrogen bond OH⋯N, 2-TRP1, 1-TRP1 and 1-TRP2, are the most stable forms with the calculated abundance of 83.4%, 10.3% and 6.0%, respectively. The presented FTIR results allow identification and characterization of these species. Several hydrogen bond parameters such as OH bond distance, νOH wavenumber shift and occupancy of the antibonding σ^∗(OH) orbital were found to be linearly related with the estimated interaction energy.