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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - IsoMS (Mass Spectrometry of Isomeric Ions)

Teaser

Summary

The IsoMS project focuses on development of mass-spectrometry tools for studying reaction mechanisms. The first part aims in development of a method for direct correlation between solution chemistry and gas-phase mass spectra. The pressure gap between formation of reaction intermediates in solution and their gas-phase detection is one of the biggest questions in mass spectrometric approach to study reactions. To tackle this question, we have designed a method called â€œDelayed reactant labelingâ€. We have shown that this method can be used to track intermediates in gold(I) catalyzed reactions. Gold containing intermediates in solution have half-lives on the order on minutes and their formation and degradation in solution can be directly tracked by mass spectrometry (e.g. Org. Biomol. Chem. 2017, 15, 7841). We have also developed a method to track fast palladium-catalyzed reactions (Organometallics 2017, 36, 2072).
The second part of IsoMS is devoted to the implementing of ion spectroscopy as an analytical tool. We have shown that our approach of helium tagging infrared photodissociation (IRPD) spectroscopy can be used to characterize reactive hypervalent metal complexes (e.g. J. Am. Chem. Soc. 2017, 139, 2757 or Chem. Commun. 2017, 53, 8786). We cooperate with several leading laboratories in bioinorganic and organometallic chemistry on further dissemination of this method and broadening of its analytical scope.
Another part of IsoMS is devoted to probing of chemical reactivity in our low temperature trap. We have made a breakthrough in the investigation of the prototypical system FeO+ + H2. This system laid grounds to the two-state reactivity concept and the key question was whether the energy barrier or rather intersystem crossing it the rate determining step of this reaction. Until our work, the rate constants for this reaction were known in the temperature range down to 100 K. We were able to measure the rate constants down to 5 K. In addition, for the first time we measured IRPD spectra of an in-trap formed reaction intermediate. It was possible to stabilize the initial reaction complex [H2FeO]+ and obtain its IRPD spectrum by the helium tagging method (ChemPhysChem. 2016, 17, 3723).
Next to the reactivity probing with neutral gases, we have also started to investigate photochemical reactivity. We have implemented measurements of visPD and UVPD spectra with our setup (J. Mol. Spec. 2017, 332, 52). Recently, we have shown that by combination of IRPD and visPD spectroscopies, we can study molecular switching in the ion trap (Phys. Chem. Chem. Phys. 2018, DOI: 10.1039/C8CP00096D). We have also investigated photodissociation processes in dependence of temperature. We were able to show how temperature influences the electronic state population of iron(II) azide complexes and thus determine the outcome of their photochemical fragmentation (Angew. Chem. Int. Ed. 2017, 56, 14057).
In general, IsoMS project successfully proceeds along the lines to implement ion spectroscopy as an analytical tool and to enhance its scope, to broaden the use of cryogenic trapping for investigation of chemical reactions and finally, to connect this research in the gas phase with the processes in the condensed phase.

Work performed

The project is divided to four work packages. Three work packages are focused on reaction mechanisms or reaction intermediates. One work package is devoted to technological development of the cryotrapping instrumentation.
WP1: We are working on implementation of Delayed reactant labeling for studying reaction mechanisms in the condensed phase. We have published a paper devoted to gold catalysis (on invitation in a special issue, Org. Biomol. Chem. 2017, 15, 7841). Further, we have developed an alternative approach to obtain solution kinetics of rapidly formed palladium complexes (Organometallics 2017, 36, 2072).
WP2: This work package is probably the fastest proceeding part. We have implemented helium tagging infrared dissociation (IRPD) spectroscopy as a common tool to investigate structure of reaction intermediates in all projects that we are doing. Further, we cooperate with a broad range of scientists from other fields to use IRPD spectroscopy as an analytical tool. We have published a methodology paper demonstrating correlation of gas-phase data with solution data and showed additional capabilities of our methods (J. Am. Chem. Soc. 2017, 139, 2757). Many collaborations for this WP arise from the COST actions ECostBio and CHAOS.
WP3: This work package is devoted to extending cryotrapping instrument with an ion mobility capability. We do not want to slow down the progress in other work packages, therefore we have decided to construct another cryotrapping instrument for further technological development. This part of the project will be concentrated in the second reporting period.
WP4: This workpackage is devoted to the investigation of reactions in our cryogenic trap. We have investigated the FeO+ + H2 reaction. Until our work, the rate constants for this reaction were known in the temperature range down to 100 K. We were able to measure the rate constants down to 5 K. In addition, we have, for the first time, measured IRPD spectra of an in-trap formed reaction intermediate. It was possible to stabilize the initial reaction complex [H2FeO]+ and obtain its IRPD spectrum by the helium tagging method (ChemPhysChem. 2016, 17, 3723). Further, we have decided to broaden the program also for photochemical reactions. We have shown that we can study isomerizations (J. Mol. Spec. 2017, 332, 52) and photofragmentations (Angew. Chem. Int. Ed. 2017, 56, 14057).

Final results

With all workpackages we aim to go beyond the state of the art. In WP1 we expect to develop a simpler way for evaluation of the data so that the method is available to larger amount of researchers. We expect to have a simple program for data evaluation. Further, we want to apply the method to study dynamic processes in solution. In WP2, we expect to implement IRPD spectroscopy as analytical tool. It is happening already, but in three more years the implementation will further advance. In WP3, we expect to show a new approach to ion mobility. We will test our originally proposed idea. Nevertheless, several new approaches appeared from the time of writing the proposal. It may turn out that one of the systems presented by other researchers would be more efficient. In that case, we will probably modify our scheme (hence, this WP will probably represent just a technological upgrade of our system). Finally, in WP4 we will continue with studying of photochemical reactions. Our system is ideally suited for these reactions and promises break-through results. We will also modify the gas-inlet systems to make reactions with additional gases in the cryotrap. We plan to investigate carbonylation reactions and other reactions proposed in the project.
Potential impact: Development of mass spectrometry methods in my laboratory will provide more tools to investigate chemical reactions. It will bring new knowledge about organic, organometallic, bioinorganic and other reactions. Further, it will broaden the analytical method selection available for scientists working with reactive compounds.