Ultrafast photochemistry of a molybdenum carbonyl–nitrosyl complex with a triazacyclononane coligand. Issue 42 (22nd October 2021)

• Record Type: Journal Article
• Authors: Gessner, Niklas; Bäck, Anna K.; Knorr, Johannes; Nagel, Christoph; Marquetand, Philipp; Schatzschneider, Ulrich; González, Leticia; Nuernberger, Patrick
• Is Part Of: Physical chemistry chemical physics. Volume 23:Issue 42(2021)
• Page Start: 24187
• Page End: 24199
• Publication Date: 2021-10-22
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/d1cp03514b
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : The photochemistry of a molybdenum complex bearing both carbonyl and nitrosyl ligands is investigated by ultrafast spectroscopy and quantum-chemical calculations with the goal to elucidate possibilities of photoinduced ligand release. Abstract : Transition metal complexes capable of releasing small molecules such as carbon monoxide and nitric oxide upon photoactivation are versatile tools in various fields of chemistry and biology. In this work, we report on the ultrafast photochemistry of [Mo(CO)2 (NO)( i Pr3 tacn)]PF6 ( i Pr3 tacn = 1, 4, 7-triisopropyl-1, 4, 7-triazacyclononane), which was characterized under continuous illumination and with femtosecond UV-pump/UV-probe and UV-pump/MIR-probe spectroscopy, as well as with stationary calculations. The experimental and theoretical results demonstrate that while the photodissociation of one of the two CO ligands upon UV excitation can be inferred both on an ultrafast timescale as well as under exposure times of several minutes, no evidence of NO release is observed under the same conditions. The binding mode of the diatomic ligands is impacted by the electronic excitation, and transient intermediates are observed on a timescale of tens of picoseconds before CO is released from the coordination sphere. Furthermore, based on calculated potential energy scans, we suggest that photolysis of NO could be possible after a subsequent excitation of an electronically excited state with a second laser pulse, or by accessing low-lying excited states that otherwise cannot be directly excited by light.