Nuclear Quadrupole Resonance Study of Proton and Deuteron Migration in Short Strong Hydrogen Bonds Formed in Molecular Complex 3,5-Dinitrobenzoic Acid–Nicotinic Acid and in Deuterated 3,5-Pyridinedicarboxylic Acid

Abstract

Temperature dependences of the 14N nuclear quadrupole resonance (NQR) frequencies have been measured in molecular complex 3,5-dinitrobenzoic acid–nicotinic acid (35DBNA) and in deuterated 3,5-pyridinedicarboxylic acid (DPDA). In deuterated DPDA, the temperature dependences of the deuterium quadrupole coupling constants and asymmetry parameters η have also been measured. In 35DBNA, the magnitude of the quadrupole coupling constant of the pyridine nitrogen agrees with the experimentally observed proton transfer. No proton exchange (O–H···N ↔ O–···H–N+) is observed. The temperature dependence of the 14N quadrupole coupling constant is analyzed in a model of a resonance hybrid of two extreme electron configurations of the molecules. The energy difference of the two extreme electron configurations is determined. In the same model, we analyzed previously published 14N NQR data of the NHO hydrogen bond in nondeuterated 3,5-pyridinedicarboxylic acid. The 14N NQR data in DPDA show the presence of a quasi-continuou...