AN NMR INVESTIGATION OF PROTON-TRANSFER DYNAMICS IN SOLID NAPHTHAZARIN-B AND NAPHTHAZARIN-C

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 T1 and T1-rho 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.