Infrared spectroscopic studies on 4-amino-6-oxopyrimidine in a low-temperature Xe matrix and crystalline polymorphs composed of double hydrogen-bonded ribbons

- IR spectra of the enol and keto forms were observed in a Xe matrix.
- Irradiation of UV light (λ > 270 nm) changed the keto to enol form.
- IR spectra were observed for AOP, hydrated, and dehydrated crystals.
- AOP and dehydrated crystals were found to be polymorphs.
- Quantum chemical calculations reproduced the observed IR spectra.