Infrared spectrum and structure of the aci-nitro form of 2-nitrophenol in a low-temperature argon matrix

2-Nitrophenol changes to the aci-nitro form by UV irradiation (λ = 248 nm). The structure is determined by a comparison of the observed infrared spectrum with the spectral patterns obtained at the DFT/B3LYP/6-31++G∗∗ level of calculation. A reverse isomerization occurs upon visible-light irradiation (λ > 450 nm).