Molecular structure of a unique UV stabilizer: Tinuvin P

The gas-phase and crystal structures of Tinuvin P were established by ab initio MP2-6-31G** level calculations and X-ray diffraction, respectively; both structures were found to include a strong intramolecular hydrogen bond. The IR transitions for this compound were determined theoretically and experimentally, as were the corresponding Raman activities. Intercyclic torsion about the N(1)-C(1) bond exhibits a very low vibrational frequency (13 cm(-1)). Based on the photophysical evidence obtained, the crystalline state of Tinuvin P may not be a suitable photophysical model for the compound in solution.