An NMR investigation of proton transfer dynamics in solid naphthazarin B and C

Abstract

Proton spin-lattice relaxation times in the laboratory and rotating frames of the B and C modifications of naphthazarin have been measured as functions of temperature and frequency. No noticeable differences between the results of the two modifications could be detected. A relaxation model in which the proton jumps between two potential minima in the vicinity of adjacent quinonoid and hydroxyl oxygens, fails to account for the observed temperature dependence of the T ₁ and T _1ρ results. Relaxation equations have been derived for a model in which the proton jumps among three potential minima. These equations give much better fits to the experimental results.