Editorial of the PCCP themed issue on “Solvation Science”

---

Abstract

The present special issue presents exciting experimental and theoretical results in the topic of “Solvation Science”, a topic that emerges from physical, theoretical, and industrial chemistry, and is also of interest to a multitude of neighboring fields, such as inorganic and organic chemistry, biochemistry, physics and engineering. We hope that the articles will be highly useful for researchers who would like to enter this newly emerging area, and that it is a valuable source for the nucleation of new ideas and collaborations to better understand the active role of the solvent in reactions.

---

The majority of chemical reactions, including many important industrial processes and virtually all biological activities, take place within a liquid environment. Solvents, of which water is surely the most prominent example,¹ are able to “solvate” molecules, thereby transferring these as “solutes” into the liquid state. Water has been dubbed the “matrix of life” in the life sciences due to its role as the ubiquitous solvent, thus, understanding solvation is crucial to unravelling biological functions in a comprehensive way.² Solvents are not only able to provide a bulk liquid phase environment for chemical reactions, they also have the ability to wet extended surfaces, such as lipid membranes or metal electrodes, thereby creating interfaces.⁴

An in-depth understanding of solvation at the fundamental level of chemistry, physics and engineering is essential to enable major advances in key technologies in order to reduce pollution, increase the efficiency of energy conversion and storage, prevent corrosion and enhance drug delivery, to name but a few challenges to our modern day society. Therefore, the time has come to develop a universal concept of solvation which not only describes solvents in general, but is additionally able to predict the properties of new solvent systems. In order to achieve this goal, physical chemistry plays a crucial role, as it not only links chemistry and physics, but also reaches biology and engineering – disciplines that are interested in and might profit from a bottom-up molecular understanding of solvation.

Solvation, as one of the core topics in chemistry, has been the subject of extensive research not only for decades, but for centuries. In addition, solvation processes are not exclusively the focus of chemists, but more recently have also attracted considerable attention from physicists, engineers and biologists. Each sub-community, however, has tended to develop its own viewpoints, models and wisdom to cope with their own challenges in developing the most efficient solvent for a specific case. In addition, these separate approaches are typically of an empirical, macroscopic and descriptive nature, as opposed to being rational, molecular and predictive. Solvents for chemical reactions, for instance, are often selected based on a broad empirical database, using, for example, the famous linear solvation free energy relationship.⁶ Alternatively, continuum solvation concepts, which neglect the molecular nature of solvents, are widely used in computer simulations due to their numerical efficiency.⁷ However, in most cases, expensive and time-consuming trial and error experiments are still necessary to find the optimum solvent. Continuing to depend on this trial and error strategy might well result in researchers missing the best solutions to the scientific challenges mentioned above.

Up to now, there has been a broad consensus in the literature that solvents are inert media for different molecular processes. Transcending this traditional view, solvents are now increasingly recognized as playing active roles in their own right, ranging from solvent-mediated to solvent-controlled and even to solvent-driven processes.^3,8

The most recent advances, for instance, in liquid-state laser spectroscopy, scanning probe microscopy and computer simulations of solvent systems including chemical reactions, herald a new era in the understanding and description of solvation. Exemplarily, it is now possible to observe chemical reactions induced by the stepwise microsolvation of a solute, starting with a single water molecule,⁹ and to directly measure the long-range correlated motions of the hydration water network around proteins or enzymes at THz frequencies.^10,11 Furthermore, ab initio molecular dynamics can now be used as a “Virtual Lab” to generate unprecedented new insights into the mechanisms of chemical reactions under wet-chemical conditions,¹² including those occurring at high temperatures, at extreme pressures and on catalytic surfaces.¹³ The structural dynamics of more complex solvation phenomena can be simulated using advanced polarizable force fields, reactive neural network potentials and hybrid all-atom/coarse-grain techniques.^14–16 Quantum mechanics/molecular mechanics approaches offer a fascinating view into the impact of functional water molecules on enzymatic reactions,¹⁷ whereas fully quantum-mechanical simulation techniques allow the quantification of nuclear quantum effects on the water structure, dynamics and chemical reactions.¹⁸

Biological processes, which have recently been recognized as being strongly dependent on or even driven by solvent effects, are increasingly studied with a focus on their coupling to the dynamics of solvent water,^19–21 which is enabled by significant experimental and theoretical advances. Pressure perturbation techniques have turned out to be a most valuable approach to understanding biomolecular solvation.^22,23 Last but not least, solvation at the air–water interface, wet solid surfaces, and catalytic processes at electrolyte–electrode interfaces can now be investigated in unprecedented molecular detail.^5,24–28 Thus, a molecular level-based bottom-up description of solvation, up to industrial applications, has come within reach by combining such experiments and simulations with tailored syntheses and chemical engineering in a cross-disciplinary approach.

In conclusion, “Solvation Science” should be identified and treated as an autonomous cross-disciplinary field, akin to Materials Science or Neuroscience, in which solvent molecules are considered to be functional units employed as active species in solvent-mediated and -controlled processes, rather than being only inert and passive spectators. This research encompasses investigations of the complex interplay between solutes, ranging from simple ions to enzymes and electrode surfaces, and solvents such as water, supercritical carbon dioxide or ionic liquids.

We would like to thank all contributors to this themed issue and the editorial team for their help and patience.

References

1. P. Ball, H₂O: A Biography of Water, Weidenfeld & Nicolson, London, 1999; H₂O: Biographie des Wassers, Piper Verlag, München, 2001.
2. P. Ball, Chem. Rev., 2008, 108, 74–108.
3. W. Sander, S. Roy, I. Polyak, J. M. Ramirez-Anguita and E. Sanchez-Garcia, J. Am. Chem. Soc., 2012, 134, 8222–8230.
4. P. Ball, Nature, 2003, 423, 25.
5. M. Mehlhorn and K. Morgenstern, Phys. Rev. Lett., 2007, 99, 246101.
6. C. Reichardt, Solvents and Solvent Effects in Organic Chemistry, Wiley-VCH, Weinheim, 2003.
7. B. Mennucci and R. Cammi, Continuum Solvation Models in Chemical Physics: From Theory to Applications, Wiley-VCH, Weinheim, 2008.
8. P. Ball, Nature, 2011, 478(7370), 467–468.
9. A. B. Wolk, C. M. Leavitt, E. Garand and M. A. Johnson, Acc. Chem. Res., 2014, 47(1), 202–210.
10. M. Heyden, J. Sun, S. Funkner, G. Mathias, H. Forbert, M. Havenith and D. Marx, Proc. Natl. Acad. Sci. U. S. A., 2014, 107, 12068.
11. V. Conti Nibali and M. Havenith, J. Am. Chem. Soc., 2014, 136(37), 12800–12807.
12. L. Vilciauskas, M. E. Tuckerman, G. Bester, S. J. Paddison and K. D. Kreuer, Nat. Chem., 2012, 4(6), 461–466.
13. E. Schreiner, N. N. Nair and D. Marx, J. Am. Chem. Soc., 2008, 130, 2768.
14. O. Demerdash, E. H. Yap and T. Head-Gordon, Annu. Rev. Phys. Chem., 2014, 65, 149–174.
15. T. Morawietz and J. Behler, J. Phys. Chem. A, 2013, 117(32), 7356–7366.
16. T. A. Wassenaar, H. I. Ingolfsson, M. Prieß, S. J. Marrink and L. V. Schäfer, J. Phys. Chem. B, 2013, 177(13), 3516–3530.
17. H. M. Senn and W. Thiel, Angew. Chem., Int. Ed., 2009, 48, 1198.
18. S. Habershon, D. E. Manolopoulos, T. E. Markland and T. F. Miller, Annu. Rev. Phys. Chem., 2013, 64, 387–413.
19. C. Y. Cheng, J. Varkey, M. R. Ambroso, R. Langen and S.-I. Han, Proc. Natl. Acad. Sci. U. S. A., 2013, 110(42), 16838–16843.
20. M. Grossman, B. Born, M. Heyden, D. Tworowski, G. B. Fields, I. Sagi and M. Havenith, Nat. Struct. Mol. Biol., 2011, 18(10), 1102–1108.
21. F. Sterpone, G. Stirnemann and D. Laage, J. Am. Chem. Soc., 2012, 134(9), 4116–4119.
22. M. A. Schroer, J. Markgraf, D. C. F. Wieland, C. J. Sahle, J. Möller, M. Paulus, M. Tolan and R. Winter, Phys. Rev. Lett., 2011, 106(17), 178102.
23. J. Möller, S. Grobelny, J. Schulze, S. Bieder, A. Steffen, M. Erlkamp, M. Paulus, M. Tolan and R. Winter, Phys. Rev. Lett., 2014, 112(2), 028101.
24. G. S. Parkinson, Z. Novotny, P. Jacobson, M. Schmid and U. Diebold, J. Am. Chem. Soc., 2011, 133(32), 12650–12655.
25. H.-J. Li, Y.-D. Li, M. T. M. Koper and F. Calle-Vallejo, J. Am. Chem. Soc., 2014, 136(44), 15694–15701.
26. A. M. Jubb, W. Hua and H. C. Allen, Annu. Rev. Phys. Chem., 2012, 63, 107–130.
27. J. Carrasco, A. Hodgson and A. Michaelides, Nat. Mater., 2012, 11(8), 667–674.
28. J. Wiebe and E. Spohr, Beilstein J. Nanotechnol., 2014, 5, 973–982.

---