Two-Step Photon Absorption Driving the Chemical Reaction in the Model Ruthenium Nitrosyl System [Ru(py)₄Cl(NO)](PF₆)₂·¹/₂H₂O

Abstract

International audienceVarious systems contg. the [ML5NO] mol., where M = Fe, Ru, ... and L = F, Cl, ..., exhibit switching under continuous light (CW) irradn. between the ground-state nitrosyl (GS), isonitrosyl (MSI), and side-on (MSII) configurations. The metastable populations, however, are often limited to a few percent. The [Ru(py)4Cl(NO)](PF6)2·1/2H2O system is thus a remarkable model compd. as the GS to MSI transformation is nearly complete in a single crystal. A predominant two-step photon absorption process during GS to MSI switching under blue light is revealed by visible absorption spectroscopy, although a low concn. of the transient species hinders the detn. of this process by the structural signature. During the depopulation of MSI, both two-step and direct processes are evidenced under red CW irradn. Different intermediate visible spectra revealing transient species during GS to MSI and the reverse photochem. processes are discussed in relation to MSII properties

Establishing the Two-Photon Linkage Isomerization Mechanism in the Nitrosyl Complex trans-[RuCl(NO)(py)4]2+ by DFT and TDDFT

“…This is consistent with the impossibility of observing MS2 when irradiation is performed at 782 nm; i.e., MS2 is simultaneously produced and used; hence, it does not accumulate. 26 As described before, depending on the excitation wavelength, excitation of MS2 to an excited singlet S n can lead to the population of either 3 MS2 or 3 GS. The very fact that, at the end of the process, a pure GS orange crystal is obtained implies that, at this wavelength (red light), the system evolves mainly to 3 GS (steps j and k).…”

Linkage Photoisomerization Mechanism in a Photochromic Ruthenium Nitrosyl Complex: New Insights from an MS-CASPT2 Study

“…13,14,15,16,17,18 Among these systems, ruthenium nitrosyl complexes have attracted growing interest over the past two decades, not only owing to their photochromic properties but also because of their capability to photorelease nitric oxide. 19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42 Despite extensive experimental investigations, the mechanism for these two competing processes remained unclear until recently. 43 Computational studies investigating the linkage photoisomerization mechanisms of metal complexes remain relatively scarce owing to the difficulty to compute the excited-state potential energy landscape in such systems.…”

“…50 On account of these results, a complex sequential two-photon photoisomerization mechanism involving nonadiabatic processes was proposed 50 and later confirmed experimentally. 41 As illustrated in Figure 1, the most stable N-bonded ground-state isomer (denoted GS) absorbs a blue light photon, which brings the system in excited singlet metal-to-ligand charge transfer ( 1 MLCT) states. These states are assumed to quickly relax by intersystem crossing (ISC) due to significant spin-orbit coupling (SOC) and by internal conversion (IC) to the lowest triplet MLCT excited state ( 3 MLCT) leading to the N-bonded triplet state 3 GS.…”

“…35,36,38 This sequential two-photon absorption mechanism was recently confirmed by visible absorption spectroscopy. 41…”

Synthesis of the Ruthenium Nitrosyl Complex with Coordinated Ammonia and Pyridine at Room Temperature

“…The MS2 state serves as an intermediate in the GS ‐to‐ MS1 photoreaction. The two‐step nature of it was confirmed at room temperature and at 100 K . The MS1 state of the complex 1 was generated at 80 K with help of 445‐nm light‐emitting diode.…”