Laboratory operando investigation of novel 3d metals complexes with valence tautomerism

From 01.10.2020 till 01.10.2022
Grant holder: Alexander Soldatov
Responsible: Svetlana Shapovalova

Valence tautomers are characterized by different electron density distributions, in which the transfer of electrons from a metal to a ligand provides the interconversion of tautomers. These compounds are unique model systems that can help in the study of electron transfer mechanisms and find application as sensors, displays or storage devices and fast optical switches. The aim of this study is the development of operando methods for the investigation of complexes with valence tautomerism and the study of novel 3d metals complexes (Co and Mn) with redox-active ligands under light and temperature exposure. During the project, specialized cells will be developed for recording X-ray and optical absorption spectra at various temperatures based on laboratory devices. Measurement of the low-temperature UV-Vis and XANES spectra, confirming the presence of temperature excited valence tautomerism and a quantitative analysis of the structural changes of complexes upon cooling are planned. Additional theoretical modelling of the atomic and electronic structures of metal complexes with redox-active ligands using different exchange-correlation functionals will allow to choose the optimal potential based on comparisons with experiments and will help to obtain the geometric parameters of various spin states. The influence of the solvent on the result of geometric optimization and stability energy will be analyzed, which is an important issue because the behavior of the system in solution, where the molecules interact weakly with each other, differs sharply from their behavior in the crystal. During the analysis of optical and X-ray spectra, we will use the existing and develop a new machine learning method for the analysis of spectra from different energy ranges. Based on the data obtained in a static mode, samples with the best properties will be selected and investigated using time-resolved UV-vis spectroscopy. This will make it possible to detect and analyze intermediate short-living forms that exist before the system enters a high-spin metastable state, as well as processes of relaxation of photoexcited states. The implementation of this project will allow us to create a laboratory technique for operando diagnostics of complexes with valence tautomerism, to determine the features of new complexes and the possibility of their practical application.