Photoinduced linkage isomers in a model ruthenium nitrosyl complex: Identification and assignment of vibrational modes

Photoinduced NO-linkage isomers were investigated in the solid state of labelled trans-[Ru((NO)-N-14/15)(py(4))F](ClO4)(2) complex by combined IR-spectroscopy and DFT calculations. Based on the experimental data and the DFT calculations of this isotopically labelled (NO)-N-14/15 nitrosyl compound, we present a complete assignment of the vibrational bands of three nitrosyl linkage isomers in a range from 4000 to 200 cm(-1). The calculated IR-spectra match well with the experimental data allowing reliable assignment of the vibrational bands. The structural change from the Ru-NO (GS) to the Ru-ON (MS1) and Ru-eta(2)-(NO) (MS2) linkage configuration leads to the downshift of the nu(NO) and nu(Ru-(NO)) bands, and a corresponding increase of the energy of the nu(Ru-F) band. The shift of the bands corresponds to the change of the Ru(NO) and Ru-F bond lengths: increase of the Ru-(NO) bond length leads to the decrease of the energy of the nu(Ru-(NO)) band; decrease of the Ru-F bond length leads to the increase of the energy of the nu(Ru-F) band. These observations can be extrapolated to the family of related nitrosyl complexes and therefore be used for the qualitative prediction of the Ru-(NO) and Ru-Ltrans-to-NO bond lengths of different linkage isomers in the framework of one complex. While the formation of linkage isomers is a reversible process, long-time irradiation sometimes induces irreversible reactions such as the release of NO. Here, we show that the photolysis of trans-[Ru((NO)-N-14/15)(py(4))F](ClO4)(2) in KBr pellets may lead to the release of nitrous oxide N2O, conceivably through the formation of a {Ru-(kappa(2)-ONNO)} intermediate. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Photoinduced NO-linkage isomers in a labelled trans-[Ru((NO)-N-14/15)(py(4))F](ClO4)(2) complex were investigated in the solid state using IR-spectroscopy and DFT calculations. The experimental data and calculations allowed for a complete assignment of vibrational bands and provided insights into the structural changes leading to the downshift of certain bands. Long-time irradiation may induce irreversible reactions, such as the release of NO or nitrous oxide N2O.