Development of novel physical properties derived from proton-dynamics in hydrogen-bonded molecular crystals

这个项目的目的是开发氢键分子晶体中质子动力学产生的新的物理性质。有两个主要的主题需要调查1。β-羟基苯丙酮互变异构化介电性能机理的阐明：用X射线单晶分析确定了3-羟基苯丙酮类化合物的氢键结构，并用高分辨固体核磁共振(CP/MAS)研究了这些化合物在晶态下发生互变异构化的可能性。(1)得到了3-羟基苯丙酮的倍频活性晶体。羟基苯酮形成了一维氢键排列，O-O距离较短(2.58A^ﾟ)。(2)介电常数测量发现2-羧基-3-羟基苯丙酮的顺电行为。该晶体在40K时表现出反铁电转变。偶极矩的转换速率大于10 GHz。(3)基于CP/MAS和介电测量，发现9-羟基苯丙酮(相II，255-280K)的无序晶体结构来源于动态起源。该分子不仅在晶体中经历了快速的互变异构化，而且还经历了120ﾟ的跳跃运动，并表现出顺磁行为。氢键对分子导体输运性质的静态和动态调制。制备了由氢键连接的各种反离子体系的Ni(Dmit)_2络合物。其中，含H_3O~+-H_2O-CH_3CN的Ni(Dmit)_2络合物的电导率在230-300K温度范围内表现出滞后现象。这种反常现象可以用在这个温度范围内熔化的过冷水分子和氧离子引起的动力学扰动来解释。这一现象可能导致一种基于在固态中发生的动态过程来控制物理性质的新方法。

This project aims at developing novel physical properties derived from proton dynamics in hydrogen bonded molecular crystals. There are two main topics to be investigated.1. Elucidation of mechanism of dielectric property derived from tautomerization of beta-hydroxyenones.Hydrogen bond patterns of 3-hydroxyenones, such as 3- or 9-hydroxy phenalenones were determined by X-ray crystallographic analysis and the possibility of tautomerization of these compounds in the crystalline state were investigated by high resolution solid state ^<13>C NMR (CP/MAS) measurements.(1) The SHG active crystal of 3-hydroxyphenalenone was obtained. Hydroxyenone forms a one-dimensional hydrogen-bonded array with short O-O distances (2.58A^^ﾟ).(2) Paraelectric behavior of 2-carboxy-3-hydroxyphenalenone was discovered by dielectric constant measurements. The crystal exhibits antiferroelectric transition at 40K. The switching rate of dipole moment is faster than 10GHz.(3) The disordered crystal structure of 9-hydroxyphenalenone (Phase II 255-280K) was found to be derived from a dynamic origin based on CP/MAS and dielectric measurements. The molecule undergoes not only a rapid tautomerization but also a 120ﾟ jumping motion in crystals and exhibits a paramagnetic behavior.2. Static and dynamic modulation of hydrogen bonds upon the transport property of molecular conductors.Ni(dmit)_2 complexes involving various counter ion systems connected by hydrogen bonds were prepared. Among them, temperature dependence of conductivity of the Ni(dmit)_2 complex carrying H_3O^+-H_2O-CH_3CN as a counter ion system exhibits a hystereses in the temperature range between 230 and 300K. The anomaly may be explained in terms of the dynamical disturbance caused by supercooled water molecules and oxonium ions which melt in this temperature range. The phenomenon may lead to a novel methodology of controlling physical properties based on dynamic processes which take place in the solid state.