Chemists of St Petersburg University have discovered a new factor that affects the solubility of organometallic compounds. The discovery will create new drugs, as well as components of microelectronics and light-emitting devices.

Solubility is the ability of one substance to mix with another, forming homogeneous systems (solutions). Most of the chemical reactions take place in solutions, moreover, in the overwhelming majority of cases, the structure of substances is also studied in them. That is why the solvent should not only dissolve the substances well, but also be able not to react with them. This problem is especially relevant for organometallic compounds, which have an extremely high ability to enter into a variety of chemical transformations.

The results of the study, supported by the RFFR, are published in the journal Angewandte Chemie.

At the same time, organometallic compounds are used in many fields, including pharmaceuticals. They exhibit a variety of types of biological activity, so they themselves can be part of the drugs, as well as being catalysts for many chemical reactions.

Traditionally, the work with poorly soluble compounds is reduced to an increase in the volume of the solvent. As a result, the cost of the product increases several-fold. Scientists of St Petersburg University put forward the hypothesis that one of the approaches to increasing solubility can be associated with the use of special additives — compounds that form multiple specific weak contacts with a soluble compound, facilitating its transition into solution.

«Investigating the solubility of the compounds of platinum metals, we have found that when in the structure of the solvent, such as dichloromethane, chlorine atoms are replaced with iodine atoms, a sharp increase in solubility is observed. We have established that in this case the key factor increasing the solubility is the specific weak interaction between the solvent and the compound — the halogen bond,» said Mikhail Kinzhalov, the first author of the work and Associate Professor of St Petersburg University.

The nature of the halogen bond was established about 20 years ago, but its effect on the solubility of substances has not been studied. Thus, chemists of St Petersburg University have discovered a fundamentally new way to control the solubility of compounds. As a result of a series of experiments, scientists have discovered that diiodomethane perfectly dissolves many classes of organometallic compounds with different structures. Diiodomethane is chemically inert to organometallic compounds, and when used, an increase in solubility for 2-15 times is observed compared to traditional solvents — trichloromethane (chloroform) and dichloromethane.

The results of the study will help chemists optimise the synthesis conditions, and also simplify the research of substances in order to understand their structure. In the future, the discovery made by scientists of St Petersburg University will increase the arsenal of organometallic compounds that can be used in pharmaceutics, electronics and applied chemistry.