Microscopic Characteristics And Potential Applications Of Hydrogen Bonds In Inorganic Solids

Hydrogen bond is one of the most important intra- and inter-molecular interactions and plays crucial roles in biological processes and solution systems. In some hydrogen-bonded functional materials, such as ferroelectrics and piezoelectrics as well as some nonlinear optical crystals, the role of hydrogen bonds is of great importance. Recently, the deliberate use of hydrogen bonds as a means of connecting molecular building blocks has been an intriguing approach in crystal engineering to produce functional materials with unique properties. Therefore, knowledge on the fundamental properties of hydrogen bonds can be extremely useful.In the first part of the current work, various types of hydrogen bonds as well as the experimental and theorical researches on hydrogen bonds were introduced.In the second part, structural characteristics of O-H…O hydrogen bonds in inorganic crystals were comprehensively studied.The direction and distance preference of hydrogen bonds were systematically analyzed and new bond valence parameters were proposed for O-H…O bonds in inorganic crystals. These parameters can be used to properly evaluate the hydrogen bond strengths and provide some information on quantitatively tuning hydrogen bond strengths in crystals. Microscopic characteristics of hydrogen bonds in Mi-OH2…O (M is the metal cation coordinated to water molecule and i is the number of M) systems were comprehensively studied. It is shown that the original O-H and H…O bond lengths of each hydrogen bonding system are evidently influenced by the crystalline environment. Furthermore, hydrogen bonding capabilities of water molecules coordinated to various metal cations were properly estimated, which provides a gudience to tune hydrogen bond strength by choosing different coordinating cations. A comprehensive analysis was also performed on the N-H…O hydrogen bonds in NH4+…O■0 systems and exact bonding behaviors of the constituent N-H and H…O bonds were explored. It is suggested that materials design by employing powerful functional groups, such as hydrogen bonding systems, may be done on the basis of a complete consideration of all components of the system.Considering the effect of the crystalline environments on the original O-H lengths in solids, a general equation for do parameters relating to the corresponding bond lengths was proposed which clearly expresses the different sensitivities of the O-H and H…O bonds on the crystalline environments. Accordingly, the valence electron distribution of hydrogen was properly calculated which may be exploited to probe the physical nature of hydrogen bonds in inorganic crystals.The study was further extended to multifurcated hydrogen bonds which exist widely in inorganic solids. On the basis of the force analysis of the H+ion within O-H…O system in inorganic crystals, a method was proposed to calculate the distribution of the valence electron of H atom among each constituent bond. The O-H and H…O bonds are treated dividually. Combining with the unique geometry and physical properties of hydrogen bonds, this method provides an effective approach for dealing with hydrogen bonds in complex inorganic crystals and even provides valuable theoretical guidance for designing and assembling new functional materials with given chemical and physical properties by use of hydrogen bonds.