Ultrafast X-ray Solution Scattering Reveals Different Reaction Pathways in the Photolysis of Triruthenium Dodecacarbonyl (Ru3(CO)12) after Ultraviolet and Visible Excitation
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- 作者：Qingyu Kong ; Jae Hyuk Lee ; Kyung Hwan Kim ; Joonghan Kim ; Michael Wulff ; Hyotcherl Ihee ; Michel H. J. Koch
- 刊名：Journal of the American Chemical Society
- 出版年：2010
- 出版时间：March 3, 2010
- 年：2010
- 卷：132
- 期：8
- 页码：2600-2607
- 全文大小：475K
- 年卷期：v.132,no.8(March 3, 2010)
- ISSN：1520-5126
文摘
Ultrafast (ps) time-resolved X-ray scattering was used to study the structural dynamics of Ru3(CO)12 in cyclohexane after photolysis at 260 nm. Two intermediates form after 100 ps at the onset of the reaction: Ru3(CO)10 for the CO loss channel and Ru3(CO)11(μ-CO) for the metal−metal cleavage channel. In our previous study at 390 nm, by contrast, three intermediates were observed simultaneously at the onset of the reaction that all relax back to Ru3(CO)12 with different lifetimes. The major difference between photolysis at 260 and 390 nm is that in the first case Ru3(CO)10(μ-CO) is formed by bimolecular recombination of Ru3(CO)10 with a free CO in 50 ns, whereas in the second case it forms directly from Ru3(CO)12 at the onset of the reaction. The differences between the photofragmentation pathways are related to the absorption bands available at the two wavelengths. The extrema in the difference radial distribution functions (RDFs) are unambiguously assigned by decomposing the total signal into contributions from the solutes, the solvent and the solute−solvent cross-terms, and also contributions from each candidate species. The difference RDFs reveal the depletion of Ru−Ru bonds (2.88 Å) in the initial Ru3(CO)12 molecule and formation of Ru3(CO)10 as the major photoproduct. The high-resolution X-ray (88 keV) scattering pattern of pure liquid C6H12 indicates that the solvent dynamics at early time delays is due to broadening of the intermolecular interatomic correlations at constant volume, whereas during thermal expansion at longer time delays, it results from shifts in these correlations.