THE FIRST DIRECT-DETECTION OF RAPID MIGRATION OF ACIDIC PROTONS BETWEEN HETEROPOLYANIONS IN H3PW12O40-CENTER-DOT-NH(2)O (N-LESS-THAN-6) BY P-31 NMR

The dynamic behavior of the acidic protons in a hydrated pseudoliquid phase of H3PW12O40. nH(2)O (n < 6) was analyzed by means of P-31 magic -angle spinning (MAS) NMR. With this method the ''isolated'' acidic pr otons on heteropolyanions were distinguished from protons in H3O+ and H5O2+. At 173 K, as evidenced by four P-31 MAS NMR peaks, these ''isol ated'' protons were distributed among polyanions so that heteropolyani ons directly bonding to 0, 1, 2, and 3 isolated acidic proton(s) coexi st. At 298 K, these peaks coalesced, directly demonstrating for the fi rst time the rapid migration of the isolated protons between heteropol yanions.