Hydrogen transfer in hydrogen-bonded chloranilic acid studied by 35Cl NQR I -: a 1:2 complex with 1,4-diazine

Cl-35 NQR frequencies and spin-lattice relaxation time (T-1Q) and H-1 NMR relaxation times (T-1H) in a H-bonded three molecular system, chloranilic acid-1,4-diazine (1:2) were measured to reveal H-motions in a symmetric two H-bonds in solid. A single Cl-35 NQR frequency observed implies that the time-averaged structure of chloranilic acid is roughly monovalent in accordance with pK(a) values in both acid and base. T-1H temperature dependence was explained by a single relaxation mechanism due to the correlated H-transfer in two H-bonds, while that of T-1Q yielded two relaxation processes. One of these undetected by H-1 NMR was explained by the uncorrelated Ii-transfer. (C) 2000 Elsevier Science B.V.