Solvation dynamics in water

It is worth noticing that, in contrast to what have been reported for the electron solvation dynamics in water and in alcohols at room temperature, we do not observe a hypsochromic translation of the electron absorption spectrum. 

Besides the obvious practical importance of solvation dynamics in water, from a fundamental standpoint, water offers a unique opportunity to evaluate theoretical models for solvation. Only for water have extensive molecular dynamics simulations been accomplished (see below). Also semi-empirical models for solvation dynamics, such as MSA, can be carefully examined for water because the necessary information on the dielectric dispersion 2(high level of accuracy. The results of the solvation... 

Figure 3.17 Comparison between experiment (dashed curve) and calculations combining the polarizable continuum model for solute electronic structure and continuum dielectric theory of solvation dynamics in water. SRF(t) stands for S(t) in our notation. The calculations are for a cavity based on a space-filling model of Cl53, while the experiments are for C343. The two sets of theoretical results correspond to using water e(o>) from simulation (full curve) of SPC/E water and from a fit to experimental data (dash-dotted curve). (Reprinted from F. Ingrosso, A. Tani andJ. Tomasi, J. Mol. Liq., 1117, 85-92. Copyright (2005), with permission from Elsevier).

K. Ando and S. Kato, Dielectric relaxation dynamics of water and methanol solutions associated with the ionization of /V,/V-dimcltiylanilinc theoretical analyses, J. Chem. Phys., 95 (1991) 5966-82 D. K. Phelps, M. J. Weaver and B. M. Ladanyi, Solvent dynamic effects in electron transfer molecular dynamics simulations of reactions in methanol, Chem. Phys., 176 (1993) 575-88 M. S. Skaf and B. M. Ladanyi, Molecular dynamics simulation of solvation dynamics in methanol-water mixtures, J. Phys. Chem., 100 (1996) 18258-68 D. Aheme, V. Tran and B. J. Schwartz, Nonlinear, nonpolar solvation dynamics in water the roles of elec-trostriction and solvent translation in the breakdown of linear response, J. Phys. Chem. B, 104 (2000) 5382-94. 

D. Laria and M. S. Skaf, Solvation response of polar liquid mixtures water-dimethylsulfoxide, J. Chem. Phys., Ill (1999) 300-09 T. J. F. Day and G. N. Patey, Ion solvation dynamics in water-methanol and water-dimethylsulfoxide mixtures, J. Chem. Phys., 110 (1999)... 

N. Nandi, S. Roy and B. Bagchi, Ultrafast solvation dynamics in water isotope effects and comparison with experimental results, J. Chem. Phys., 102 (1995) 1390-7. 

P. L. Geissler and D. Chandler,/. Chem. Phys., 113, 9759 (2000). Importan ce Sampling and the Theory of Nonequilibrium Solvation Dynamics in Water. 

In addition, water motion has been investigated in reverse micelles formed with the nonionic surfactants Triton X-100 and Brij-30 by Pant and Levinger [41]. As in the AOT reverse micelles, the water motion is substantially reduced in the nonionic reverse micelles as compared to bulk water dynamics with three solvation components observed. These three relaxation times are attributed to bulklike water, bound water, and strongly bound water motion. Interestingly, the overall solvation dynamics of water inside Triton X-100 reverse micelles is slower than the dynamics inside the Brij-30 or AOT reverse micelles, while the water motion inside the Brij-30 reverse micelles is relatively faster than AOT reverse micelles. This work also investigated the solvation dynamics of liquid tri(ethylene glycol) monoethyl ether (TGE) with different concentrations of water. Three relaxation time scales were also observed with subpicosecond, picosecond, and subnanosecond time constants. These time components were attributed to the damped solvent motion, seg-... 

Pant and Levinger have measured the solvation dynamics of water at the surface of semiconductor nanoparticles [48,49]. In this work, nanoparticulate Zr02 was used as a model for the Ti02 used in dye-sensitized solar photochemical cells. Here, the solvation dynamics for H2O and D2O at the nanoparticle surface are as fast or faster than bulk water motion. This is interpreted as evidence for reduced hydrogen bonding at the particle interface. 

However, picosecond resolution is insufficient to fully describe solvation dynamics. In fact, computer simulations have shown that in small-molecule solvents (e.g. acetonitrile, water, methyl chloride), the ultrafast part of solvation dynamics (< 300 fs) can be assigned to inertial motion of solvent molecules belonging to the first solvation layer, and can be described by a Gaussian func-tiona) b). An exponential term (or a sum of exponentials) must be added to take into account the contribution of rotational and translational diffusion motions. Therefore, C(t) can be written in the following form ... 

Femtosecond dynamics of the solvated electron in water studied by time-resolved Raman spectroscopy... 

When an electron is injected into a polar solvent such as water or alcohols, the electron is solvated and forms so-called the solvated electron. This solvated electron is considered the most basic anionic species in solutions and it has been extensively studied by variety of experimental and theoretical methods. Especially, the solvated electron in water (the hydrated electron) has been attracting much interest in wide fields because of its fundamental importance. It is well-known that the solvated electron in water exhibits a very broad absorption band peaked around 720 nm. This broad absorption is mainly attributed to the s- p transition of the electron in a solvent cavity. Recently, we measured picosecond time-resolved Raman scattering from water under the resonance condition with the s- p transition of the solvated electron, and found that strong transient Raman bands appeared in accordance with the generation of the solvated electron [1]. It was concluded that the observed transient Raman scattering was due to the water molecules that directly interact with the electron in the first solvation shell. Similar results were also obtained by a nanosecond Raman study [2]. This finding implies that we are now able to study the solvated electron by using vibrational spectroscopy. In this paper, we describe new information about the ultrafast dynamics of the solvated electron in water, which are obtained by time-resolved resonance Raman spectroscopy. 

Skaf MS, Ladanyi BM. 1996. Molecular dynamics simulation of solvation dynamics in methanol-water mixtures. J Phys Chem 100 18258-18268. 

F. Ingrosso, A. Tani and J. Tomasi, Solvation response in water a study based on molecular dynamics simulations and quantum mechanical calculations, J. Mol. Liq., 117 (2005) 85-92. 

S. Arzhantzev and M. Maroncelli, Polar solvation and solvation dynamics in supercritical CHF3 results from experiment and simulation, J. Phys. Chem. A, 110 (2005) 3405-13 J. S. Duan, Y. Shim and H. J. Kim, Solvation in supercritical water, J. Chem. Phys., 124 (2006). 

I. Benjamin, Chemical reactions and solvation at liquid interfaces a microscopic perspective, Chem. Rev. (Washington, D. C.), 96 (1996) 1449-75 I. Benjamin, Theory and computer simulations of solvation and chemical reactions at liquid interfaces, Acc. Chem. Res., 28 (1995) 233-9 L. R. Martins, M. S. Skaf and B. M. Ladanyi, Solvation dynamics at the water/zirconia interface molecular dynamics simulations, J. Phys. Chem. B, 108 (2004) 19687-97 J. Faeder and B. M. Ladanyi, Solvation dynamics in reverse micelles the role of headgroup-solute interactions, J. Phys. Chem. B, 109 (2005) 6732 10 W. H. Thompson, Simulations of time-dependent fluorescence in nano-confined solvents, J. Chem. Phys., 120 (2004) 8125-33. 

In this section, we review our first examinations of tryptophan probing sensitivity and water dynamics in a series of important model systems from simple to complex, which range from a tripeptide [70], to a prototype membrane protein melittin [70], to a common drug transporter human serum albumin [71], and to lipid interface of a nanochannel [86]. At the end, we also give a special case that using indole moiety of tryptophan probes supramolecule crown ether solvation, and we observed solvent-induced supramolecule folding [87]. The obtained solvation dynamics in these systems are linked to properties or functions of these biological-relevant macromolecules. 

EJ Hart and M Anbar have detailed the characteristics and the chemistry of the solvated electron in water, otherwise known as the hydrated electron and denoted by e] y or e. A number of reviews on the solvated electron are also available.In this article, we will recall briefly the main steps of the discovery and the principal properties of the solvated electron. We will then depict its reactivity and focus on recent results concerning the effect of metal cations pairing with the solvated electron. At last, we will present results on the solvation dynamics of electron. Due to the development of ultrashort laser pulses, great strides have been made towards the understanding of the solvation and short-time reactivity of the electron, mainly in water but also in polar solvents. However, due to the vast and still increasing literature on the solvated electron, we do not pretend for this review to be exhaustive. 

The solvated electron is a transient chemical species which exists in many solvents. The domain of existence of the solvated electron starts with the solvation time of the precursor and ends with the time required to complete reactions with other molecules or ions present in the medium. Due to the importance of water in physics, chemistry and biochemistry, the solvated electron in water has attracted much interest in order to determine its structure and excited states. The solvated electrons in other solvents are less quantitatively known, and much remains to be done, particularly with the theory. Likewise, although ultrafast dynamics of the excess electron in liquid water and in a few alcohols have been extensively studied over the past two decades, many questions concerning the mechanisms of localization, thermalization, and solvation of the electron still remain. Indeed, most interpretations of those dynamics correspond to phenomenological and macroscopic approaches leading to many kinetic schemes but providing little insight into microscopic and structural aspects of the electron dynamics. Such information can only be obtained by comparisons between experiments and theoretical models. For that, developments of quantum and molecular dynamics simulations are necessary to get a more detailed picture of the electron solvation process and to unravel the structure of the solvated electron in many solvents. 

Assel M, Laenen R, Laubereau A. (1999) Retrapping and solvation dynamics after femtosecond UV excitation of the solvated electron in water. J Chem Phys 111 6869-6874. 

Nandi N, Bhattacharyya K, Bagchi B. Dielectric relaxation and solvation dynamics of water in complex chemical and biological systems. Chem. Rev. 2000 100 2013-2045. 

---