Multiple light-induced NO linkage isomers in the dinitrosyl complex RuClNO2PPh32BF4 nravelled by photocrystallographic and IR analysisReport as inadecuate




Multiple light-induced NO linkage isomers in the dinitrosyl complex RuClNO2PPh32BF4 nravelled by photocrystallographic and IR analysis - Download this document for free, or read online. Document in PDF available to download.

1 CRM2 - Cristallographie, Résonance Magnétique et Modélisations 2 Ludwig-Maximilians-Universität München 3 Institut für Strukturphysik

Abstract : Multiple light-induced reversible metastable NO linkage isomers PLIs have been detected in the dinitrosyl compound RuClNO2PPh32BF4 by a combination of photocrystallographic and IR analysis. The IR signature of three PLI states has been clearly identified, with estimated populations of 59% PLI-1, 8% PLI-2 and 5% PLI-3 for a total population of the metastable state of 72%. The structural configuration of the major component PLI-1 has been derived by X-ray photocrystallography. In the ground state, the structure is characterized by a bent and a linear nitrosyl, the bent one being oriented towards the linear equatorial nitrosyl with an Ru-N-O angle of 133.88 9degrees. X-ray Fourier difference maps indicate a selectivity of the photo-isomerization process in PLI-1: only the bent NO ligand changes its position, while the linear NO is unaffected. After irradiation at 405 nm, the orientation is changed by rotation towards the Cl ligand opposite the linear NO, with an Ru-N-O angle in this new position of 109 1degrees. The photocrystallographic analysis provides evidence that, in the photo-induced metastable state, the bent NO group is attached to the Ru atom through the N atom Ru-N-O, rather than in an isonitrosyl Ru-O-N binding mode. In the IR spectra, the asymmetric NO vibrational band shifts by -33 cm-1 to a lower value, whereas the symmetric band splits and shifts by 5 cm-1 to a higher value and by -8 cm-1 to a lower value. The down shift is a clear indication of the structural change, and the small upward shift in response to the new electronic configuration of the metastable structure. Variable-temperature IR kinetic measurements in the range 80-114 K show that the decay of the PLI-1 state follows an Arrhenius behaviour with an activation energy of 0.22 eV.

Keywords : crystal structure light-induced isomerism reversible isomerism dinitrosyl compounds photocrystallography IR spectra





Author: Nicolas Casaretto - Sébastien Pillet - El-Eulmi Bendeif - Dominik Schaniel - Anna K. E. Gallien - Peter Kluefers - Theo Woike -

Source: https://hal.archives-ouvertes.fr/



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