Local force constants and charges of the nitrosyl ligand in photoinduced NO linkage isomers in a prototypical ruthenium nitrosyl complex

• Published in: Physical chemistry chemical physics : PCCP Vol. 26; no. 21; pp. 15255 - 15267
• Main Authors: Mikhailov, Artem A, Gansmüller, Axel, Konieczny, Krzysztof A, Pillet, Sébastien, Kostin, Gennadiy, Klüfers, Peter, Woike, Theo, Schaniel, Dominik
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 29.05.2024
• Subjects: Chemical Sciences; Coordination chemistry; Frequency shift; Harmonic oscillators; Isomers; Ligands; or physical chemistry; Ruthenium; Stretching; Theoretical and; Transition metals; Wavelengths; linkage isomers; nitrosyl; local force constants; infrared spectroscopy
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d4cp01374c

Photoinduced linkage isomers (PLI) of the NO ligand in transition-metal nitrosyl compounds can be identified by vibrational spectroscopy due to the large shifts of the &z.ngrt; (NO) stretching vibration. We present a detailed experimental and theoretical study of the prototypical compound K 2 [RuCl 5 NO], where &z.ngrt; (NO) shifts by 150 cm −1 when going from the N-bound (κN) ground state (GS) to the oxygen-bound (κO) metastable linkage isomer MS1, and by 360 cm −1 when going to the side-on (κ 2 N,O) metastable linkage isomer MS2. We show that the experimentally observed N-O stretching modes of the GS, MS1, and MS2 exhibit strong coupling with the Ru-N and Ru-O stretching modes, which can be decoupled using the local mode vibrational theory formalism. From the resulting decoupled pure two-atomic harmonic oscillators the local force constants are determined, which all follow the same quadratic behavior on the wavenumber. A Bader charge analysis shows that the total charge on the NO ligand is not correlated to the observed frequency shift of &z.ngrt; (NO). Photoinduced NO linkage isomers: total charges on NO are not correlated to the frequency of the NO stretching vibration. Local force constants reveal a significant change in coupling of Ru-N/O and N-O stretching vibrations.