Water is a simple molecule with many unique physical properties that are critical to life on earth. Its properties arise from its extended hydrogen-bonded network, in which water-water hydrogen bonds are constantly breaking and forming. However, in many biological systems and materials, the water network is impacted by the presence of solutes and interfaces. In this thesis, the structure and dynamics of the hydrogen bond network are examined in technologically relevant materials where water plays a key role. The systems studied include fuel cell membranes, hydrogels and concentrated salt solutions. Nonlinear infrared spectroscopy can be used to experimentally observe ultrafast motions of water as well as its structural configurations within complex chemical systems. Polarization-selective pump-probe experiments on the OD stretch of dilute HOD in water provide information on both orientational and vibrational relaxation. Orientational relaxation describes the reorientation dynamics of water molecules in the hydrogen bond network. If angular diffusion is restricted, orientational relaxation also provides insight into how water may be sterically hindered within its environment. Vibrational relaxation describes coupling of vibrational energy absorbed by the HOD molecules to its surrounding media. The vibrational lifetime provides details on the local interactions of HOD and may allow separation of distinct dynamics near different species. Two-dimensional vibrational echo experiments on HOD molecules observe the time scales for structural evolution of the surrounding environment through ultrafast vibrational frequency fluctuations. With these experimental techniques, a holistic picture of the structure and motions of the water hydrogen bond network can be acquired.
The study of liquids covers a wide range of scientific disciplines, primarily in physics and chemistry. As a result of this disparate activity the links between new developments in remote fields are seldom co-ordinated into a single conference. The objective of the present meeting was to gather together people with different forms of expertise. Previous ASI meetings on the liquid state have been held over an extended period and have occurred on a three-yearly basis. The first meeting in this series was on 'Structure and Dynamics of Liquids' in 1980 and was held on the island of Corsica. The next meeting on 'Molecular liquids: Dynamics and Interactions' was held in Florence in 1983 and was followed by 'Aqueous Solutions' at the Institut d'Etudes Scientifiques de Cargese in 1986. It therefore seemed a natural choice to select Cargese for the next meeting in 1989 and to choose a topic which emphasised a particular area of liquid state studies. Due to our own involvement in collaborative research we considered that 'Hydrogen-bonded liquids' would be an appropriate topic. One of its attractions, was that there was much new material coming from widely disparate investigations and it would be a convenient time to draw together the different strands. The particular interest in water was clearly central to this topic but it was thought desirable to set this development in the wider context of other systems in which hydrogen-bonding plays a significant role.
The hydrogen bond represents an important interaction between molecules, and the dynamics of hydrogen bonds in water create an ever-present question associated with the process of chemical and biological reactions. In spite of numerous studies, the process remains poorly understood at the microscopic level because hydrogen-bond dynamics, such as bond rearrangements and hydrogen/proton transfer reactions, are extremely difficult to probe. Those studies have been carried out by means of spectroscopic methods where the signal stems from the ensemble of a system and the hydrogen-bond dynamics were inferred indirectly. This book addresses the direct imaging of hydrogen-bond dynamics within water-based model systems assembled on a metal surface, using a scanning tunneling microscope (STM). The dynamics of individual hydrogen bonds in water clusters, hydroxyl clusters, and water-hydroxyl complexes are investigated in conjunction with density functional theory. In these model systems, quantum dynamics of hydrogen bonds, such as tunneling and zero-point nuclear motion, are observed in real space. Most notably, hydrogen atom relay reactions, which are frequently invoked across many fields of chemistry, are visualized and controlled by STM. This work presents a means of studying hydrogen-bond dynamics at the single-molecule level, providing an important contribution to wide fields beyond surface chemistry.
The Hydrogen Bond and the Water Molecule offers a synthesis of what is known and currently being researched on the topic of hydrogen bonds and water molecules. The most simple water molecular, H2O, is a fascinating but poorly understood molecule. Its unique ability to attract an exceptionally large number of hydrogen bonds induces the formation of a dense "hydrogen bond network" that has the potential to modify the properties of the surrounding molecules and their reactivities. The crucial role that water molecules play is described in this book. The author begins by providing an overview of the thermodynamical and structural properties of H-bonds before examining their much less known dynamical properties, which makes them appear as centres of reactivity. Methods used to observe these components are also reviewed. In the second part of the book the role played by the dense H-bond network developed by H2O molecules is examined. First in ice, where it has important atmospheric consequences, then in liquid water, and finally in macromolecules where it sheds some original light on the fundamental question "How is it that without water and hydrogen bonds life would not exist?". This book will be of interest to researchers in the fields of physics, chemistry, biochemistry and molecular biology. It can also serve as a teaching aid for students attending course in chemical physics, chemistry or molecular biology. Engineers involved the water industry would benefit from reading this book, as would scientists working in pharmaceutics, cosmetics and materials. * overview of what is known and being researched on the topic of hydrogen bonds and water molecules * reviews methods used to observe interactions between water molecules and hydrogen bonds * examines role of H-bond network developed by H2O molecules
This book gives an extensive description of the state-of-the-art in research on excited-state hydrogen bonding and hydrogen transfer in recent years. Initial chapters present both the experimental and theoretical investigations on the excited-state hydrogen bonding structures and dynamics of many organic and biological chromophores. Following this, several chapters describe the influences of the excited-state hydrogen bonding on various photophysical processes and photochemical reactions, for example: hydrogen bonding effects on fluorescence emission behaviors and photoisomerization; the role of hydrogen bonding in photosynthetic water splitting; photoinduced electron transfer and solvation dynamics in room temperature ionic liquids; and hydrogen bonding barrier crossing dynamics at bio-mimicking surfaces. Finally, the book examines experimental and theoretical studies on the nature and control of excited-state hydrogen transfer in various systems. Hydrogen Bonding and Transfer in the Excited State is an essential overview of this increasingly important field of study, surveying the entire field over 2 volumes, 40 chapters and 1200 pages. It will find a place on the bookshelves of researchers in photochemistry, photobiology, photophysics, physical chemistry and chemical physics.
The book presents the fantastic world of water in all its different forms, from liquid to ice and snow. This book is amply illustrated with a large number of beautiful pictures with. Water plays a unique role in chemistry. The special properties of water are due to hydrogen bonding between the H2O molecules. The hydrogen bond is of fundamental importance in biological systems since all living matter has evolved from and exists in an aqueous environment, and hydrogen bonds are involved in most biological processes. There is a hundred times more water molecules in our bodies than the sum of all the other molecules put together.The unique properties of water are of great importance in our daily life. The origin of these special properties is often not recognized. Even among chemists and physicists, the fundamental facts are not always known. In spite of very active research, there are still many questions to be answered about the structure of liquid water, for instance.The book differs from most books on water as it covers basic facts about structure and properties as well as the influence of these properties in our daily life. Why does ice float on water? Why is the maximum density of water at 4°C? The beauty of snow crystals is amply illustrated, and many of the pictures are unique.
Covering the scope of current water research from the physical chemistry viewpoint, this long-awaited book focuses on the structure, dynamics and properties of water and solutions. The authors are chosen in such a way that teams treat each topic from both the experimental and theoretical perspective, resulting in a quantitative understanding of the so-called "anomalies" of the pure liquid. Recent experimental approaches, computer simulations and theories provide new insight into the origins of these features as well as explanations on a molecular scale. With such topics as hydrogen bonding, proton transfer reactions, water thermodynamics, structures and dynamics in all phases, this is of great interest for chemists, physicists and biologists.
Water is one of the most important substances in the world. It is used in a wide range of technologies and is an essential ingredient in all living cells we know today. The structure of water molecule is simple, yet it can form extended and versatile hydrogen bond (HB) network. This ability gives water extraordinary properties, such as high boiling and melting point. At the same time, the hydrogen bond network is not static. The constant breaking and re-forming of hydrogen bond occurs on the picosecond timescale. This dynamic network facilitates many functions of water, including ions solvation, protein folding and electricity conduction. Understanding the structure and dynamics of these processes is therefore of great importance. Ultrafast infrared (IR) spectroscopies offer a great method for accessing the sub-picosecond to picoseconds dynamics while a system in an electronic ground state. During the past two decades, hydrogen bond dynamics has been investigated extensively using ultrafast IR spectroscopies. But many questions still exist such as the effect of ions and confinement on the hydrogen bonding dynamics and the relation between the anomalous proton diffusion in dilute solution and hydrogen bonding. In Chapter 3, we examined the nature of molecular anion hydrogen bonding. The CN stretch of selenocyanate anions (SeCN-) was used as the vibrational probe in heavy water D2O. We observed the non-Condon effect on the CN stretch whose transition dipole changes with the strength of hydrogen bonding with water. In addition, HB rearrangement dynamics reported by SeCN- is almost the same as was that of the OH stretch of HOD molecules. This result shows that this anion does not perturb the surrounding HB network significantly in the low salt concentration solution. This ionic perspective is important and complements the results using OD or OH stretch of HOD molecules, which can only probe the effect of ions in a high salt concentration condition. In Chapter 4, we used SeCN- as the probe to examine water dynamics in confinement, and I focused on the nano waterpool formed in reverse micelles. The water pool is surrounded by surfactants which are further solvated by organic hydrophobic solvents. For large reverse micelle whose diameter is larger than 4 nm, the water pool is usually divided into two regions: the core region where water dynamics is like that in pure water and the interface region where water dynamics is slowed significant due to the confinement. Here we used ultrafast IR spectroscopies to measure the orientational relaxation of SeCN-, which reflects its interaction with water molecules and how "rigid" the HB network is. Based on the comparison between linear IR decomposition and ultrafast anisotropy dynamics, we proposed a three-component model of water in large reverse micelles. The interface component should be further separated into two layers. One layer corresponds to water in contact with the surfactant head group and has very slow reorientation. The other layer corresponds to water molecules whose coordinating structure still resembles that of bulk but the dynamics is slowed down due to the perturbation from confinement. In Chapter 5 and 6, hydrogen bonding dynamics in concentrated salt and acid solutions were investigated. Through electrochemical method, it was found decades ago that proton has extraordinary ion mobility, about 6 times larger than that of cations of similar sizse, such as sodium, ammonium or lithium. The great difference between them results from the cation transport mechanism. In dilute solution, the main transport mechanism of proton is through relay mechanism where the identity of proton transfers from one water molecule to another. This minimizes the physical diffusion of the atoms and greatly increases the proton mobility. The mechanism is generally called Grotthuss mechanism, which was came up with by Grotthuss in 1806 though not on the molecular level. However, the step time of a single proton transfer event between two water molecules is difficult to observe experimentally. Here we used the CN stretch of methyl thiocyanate (MeSCN) as the vibrational probe. In concentrated hydrochloric solutions, it has two frequency resolved states. One state refers to water hydrogen bonded to the nitrogen lone pair while the other state corresponds to hydronium ion hydrogen bonded to the CN. Chemical exchange phenomenon was observed between these two states. Ab initio simulation done by our collaborator shows that the proton hopping is the dominate mechanism for chemical exchange. The comparison experiment done in lithium chloride solution provides further contrast between hydronium and other metal ions. Therefore, we were able to track proton hopping in a time-resolved manner for the first time. Extrapolation to the dilute limit demonstrates that the HB rearrangement in pure water is the driving force of proton hopping in dilute solution.
The book illustrates the fascinating world of the different forms of water - from ice and snow to liquid water. The water molecule, H2O, is the second most common molecule in the Universe (behind hydrogen, H2) and ice is the most abundant solid material. Snow and ice appear in a countless large number of different shapes and with properties which can be quite different. Detailed knowledge of the properties of snow is of great importance for the Sami people involved in reindeer herding and several hundred names are used to characterize the different types. The properties of ice and liquid water are very special and unique in several respects. In contrast to most other substances, the density of ice is lower than that of liquid water, which has many very important consequences in our daily life. Water plays a unique role in chemistry and although tremendous research has been spent on this seemingly simple substance, there are still many unsolved questions about the structure of liquid water. The special properties of water are due to hydrogen bonding between the H2O molecules, and this book may be seen as a tribute to the hydrogen bond. The general properties of the hydrogen bond are treated in three separate papers. The hydrogen bond is of fundamental importance in biological systems since all living matter has evolved from and exists in an aqueous environment and hydrogen bonds are involved in most biological processes. There is a hundred times more water molecules in our bodies than the sum of all the other molecules put together. -- Provided by publisher.
