Proton dynamics in one-dimensional hydrogen-bonding system in molecular co-crystals TMP-D2ca and DMP-H2ca

The proton dynamics in one-dimensional hydrogen-bonding system in molecular co-crystals of tetramethylpyrazine (TMP) with chloranilic acid (H2ca), as well as 2,6-dimethylpyrazine (DMP) with H2ca is studied by 35Cl NQR and 2H NMR spin-lattice relaxation measurements. No transfer motion of proton between the acid and base molecules is observed in DMP-H2ca, while the motion of the acid proton is excited in TMP-H2ca and the activation energy for the motion increases from 35 kJ mol − 1 to 50 kJ mol − 1 by the deuteration.