Czech Society for Mass Spectrometry

(Czech Mass Spectrometry Conference 2018 - WeS-002)
Terminal iron(III)-oxo complexes

Rafael Navrátil ¹, Erik Andris ¹, Juraj Jašík ¹, Mayank Puri ², Miquel Costas ³, Lawrence Que, Jr. ², Jana Roithová ^1 *

1. Charles University, Prague, Czech Republic
2. University of Minnesota, Minneapolis, Unites States of America
3. University of Girona, Girona, Spain

Abstract

Terminal iron(IV)-oxo compounds are one of the best explored systems in bioinorganic and biomimetic chemistry.[1] Conversely, terminal iron(III)-oxo compounds, products of formal one-electron reduction of iron(IV)-oxo analogs, have been studied only scarcely. Herein, we report the generation of representative tetragonal and trigonal iron(III)-oxo complexes in the gas phase. Iron(III)-oxo complexes were prepared by two methods, either by oxidative cleavage of iron(II)-nitrate precursors or by one-electron reduction of iron(IV)-oxo compounds. All studied complexes were characterized by infrared and visible photodissociation spectroscopies, which provided Fe–O vibration frequencies and allowed assignment of spin states. The Fe–O vibration of the quartet state iron(III)-oxo complexes is located at the same frequency as that of their iron(IV)-oxo analogs. The position of the Fe–O vibration in the sextet state complexes is red-shifted by approximately 70 cm^-1. Therefore, the Fe–O vibration frequency reflects the spin state of iron center in terminal iron(III)-oxo compounds in contrast to iron(IV)-oxo compounds. Furthermore, we studied the effect of water coordination to the iron-oxo unit and found out that quartet state complexes undergo spin change upon water coordination. Our spectroscopic data provide a solid starting point for the identification and investigation of these reactive intermediates in the condensed phase.

* Corresponding author: jana.roithova@natur.cuni.cz

References

1. Hohenberger J. et al.: Nature Commun. 3, 720 (2012).

Acknowledgement:

The authors gratefully acknowledge financial support from the European Research Council (CoG IsoMS, No.682275).