Photogeneration of Several Linkage Isomers and Investigation of Forward and Backward Nitro-Nitrito Isomerization Processes in a Palladium Complex

• Published in: Inorganic chemistry Vol. 62; no. 14; pp. 5531 - 5542
• Main Authors: Mikhailov, Artem, Konieczny, Krzysztof A., Gladysheva, Maria, Plyusnin, Pavel, Pillet, Sébastien, Schaniel, Dominik
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 10.04.2023
• Subjects: Chemical Sciences; Cristallography
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.3c00028

Photoinduced linkage isomers (PLIs) of the nitro-ligand were generated and comprehensively characterized in a square planar unit [Pd­(NH3)3NO2]+ of the complex salts [Pd­(NH3)4]­[Pd­(NH3)3NO2]­[MOx3]·yH2O (M = Cr (Cr), Rh (Rh), Co (Co), Ox = oxalate). Structural (XRD) and spectroscopic (IR, UV–vis) investigations at 10 and 150 K allowed determining the structures of several photoinduced linkage isomers, endo-ONO (PLI1, 2) and exo-ONO (PLI3, 4) isomers generated by irradiation with 365 nm from the initial NO2 (GS), along with the assignment of the infrared (IR) bands to each structural isomer. Based on a combination of these methods, the photo- and thermally induced interplay of PLIs was investigated. Irradiation in the temperature range of 10–80 K induces the formation of both endo- and exo-ONO isomers, while increasing the temperature up to 150 K results in the formation of only endo-ONO isomers. The structural arrangement of the endo-ONO and exo-ONO PLI is strongly influenced by intermolecular interactions due to the partial occupation of a neighboring site by water molecules. The investigation of thermal dynamics of PLIs revealed that the thermal decay of the exo-ONO isomer occurs via two steps exo-ONO → endo-ONO → NO2. The kinetic parameters (E a, k 0) of both decay processes were determined together with the characteristic decay temperatures (T d) by IR spectroscopy. According to the photoinduced dynamics measured by IR spectroscopy, the mechanism of PLI formation in [Pd­(NH3)3NO2]+ could be described as NO2 → endo-ONO → exo-ONO.