Analysis on short hydrogen-bonded system formed between hetero-atoms

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In order to investigate a static and dynamic structure of strong hydrogen-bonded system, nitrogen and chlorine nuclear quadrupole resonance (NQR) frequencies and the spin-lattice relaxation times as well as single crystal X-ray diffraction have been measured in a wide temperature range for organic salts and co-crystals in which the components are connected by short hydrogen bonds. The systems undertaken are chloranilic acid-pyridine (or amine) derivatives, chloro-nitro-benzoic acid-pyridine (or amine) derivatives, which are expect to have a short hydrogen bond with a disordered hydrogen atom in it. The results are as follows: (1) disordered feature of the H atom in a one-dimensional hydrogen-boned system of chloranilic acid-morpholine (1/1) system was clarified and an anomalous temperature dependence of the NQR frequencies was analyzed by the H atom disorder; (2) hydrogen-bonding schemes in (1/1) and (1/2) compounds of chloranilic acid with pyrrolidone and piperidone were determined; (3) mechanism of the antiferroelectric-paraelectric phase transition in (1/1) compounds of chloranilic acid with 5,5'-dimethyl-2,2'-bipyridine and 1,5-naphthyridine was analyzed by temperature dependence of nitrogen NQR frequencies; (4) mechanism of the phase transition and disordering in hydrogen-bonded system of pyrimidinium hydrogen chloranilate monohydrate were clarified; (5) new hydrogen-bonded systems of chloro-nitro-benzoic acids with quinoline and phthalazine, where a short hydrogen bond exists between the acid and base molecules, were found.