NSU Scientists Conduct Unique Experiment on Molecular Structure of Ionic Liquids

Scientists at the Novosibirsk State University Laboratory for Structures and Functional Properties of Molecular Systems and the Institute of Catalysis SB RAS, Danil Kolokolov and Alexander Stepanov, together with German Professor Ralf Ludwig, studied hydrogen bonds in various ionic liquids. They found that due to the complex molecular arrangement, these substances exhibit unusual phase behavior. There have not been similar studies conducted on solid-state ionic liquids. The scope of applications for ionic liquids is diverse ranging from the chemical industry to rocket engineering.

Danil Kolokolov was invited to participate in the Humboldt Kolleg, which takes place in Novosibirsk every few years. The Novosibirsk scientist presented the results of his work on the study of molecular mobility and states of substances containing hydrogen bonds (water in a different aggregate state, alcohols, etc.) to his German colleagues.

Kolokolov, Candidate of Physical and Mathematical Sciences and Senior Research Fellow at the NSU Laboratory for Structures and Functional Properties of Molecular Systems described how the international partnership evolved,

Thanks to the Humboldt event, I met Professor Ralph Ludwig from the University of Rostock, who became interested in our capabilities and research methods. His scientific interests are ionic liquids. We had never worked on this but during our discussion it became clear that we could contribute to an understanding of how complex objects such as ionic liquids are arranged. After our German colleagues sent us samples, we started an experiment that had never been conducted before. So far, everything has turned out very well.

Ionic fluid is a liquid that only contains ions. In a broad sense, ionic liquids are any molten salt, for example sodium chloride, melted at a temperature above 800 C. Today, the term "ionic liquids" most commonly means salts whose melting point is lower than the boiling point of water, i.e. below 100 C. Salts that melt at room temperature are called “RTIL” or Room-Temperature Ionic Liquids.

The main fields for the application of ionic liquids are energy, biotechnology, chemistry, and rocket engineering. Ionic liquids belong to what are called "green solvents” that correspond to the principles of green chemistry (a scientific focus that refers to any improvement in chemical processes that positively influences ecology). Some ionic liquids, for example, 1-butyl-3-methylimidazolium chloride, are relatively effective solvents for cellulose. In classical solvents, this process occurs only under very severe conditions.

As head of the research project, Kolokolov talked about their work,

Ionic liquids are promising for use as dielectrics. For example, in car batteries, a standard dielectric is a solution of sulfuric acid and water. However, sulfuric acid is very volatile and toxic. For the battery, this presents its own problem. There can be a separate problem, the battery breaks, acid flows, and immediately there is a threat to a person. Now imagine that an ionic liquid appears that can transmit a charge, but is less volatile and toxic. We will get cleaner production that is less harmful to the environment. In order to modify ionic liquids, one must understand how they are structured and they are complicated. We still do not quite understand what the freezing temperature depends on, what their structure is in the frozen state and so on. In the course of our experiment, we discovered from the characteristics of observable data that it is possible to differentiate different ionic liquids by the type of hydrogen bonds. In addition to the bond structure, we can obtain data on molecular dynamics, and measure the rate of molecular diffusion. In the future, this can be used for quantum calculations and predicting the functional properties of these materials depending on the molecular structure.

The results of this research provided the basis for two scientific articles published in the leading general chemistry journals, “Angewandte Chemie” and “Chemical Communications”. The Novosibirsk scientists were able to demonstrate that in addition to being complex structures, ionic liquids exhibit unusual phase beh * avior: they are dynamically heterogeneous.

Kolokolov summed up their findings,

At first, it looks like a crystal. However, when you look at it from the point of view of dynamics, you see a mixture of immobile and liquid states. This is a unique observation. We were able to show that this occurs at a sufficiently low temperature (-50 ° C), until the transition to a liquid state at room temperature. This means that the rapid movement of protons in ionic liquids is possible in a frozen state.