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- Title
Visible Light-Induced Homolytic Cleavage of Perfluoroalkyl Iodides Mediated by Phosphines.
- Authors
Bracker, Mario; Helmecke, Lucas; Kleinschmidt, Martin; Czekelius, Constantin; Marian, Christel M.; Costa, Paulo Jorge; Santoro, Fabrizio
- Abstract
In an effort to explain the experimentally observed variation of the photocatalytic activity of t Bu 3 P, n Bu 3 P and (MeO) 3 P in the blue-light regime [Helmecke et al., Org. Lett. 21 (2019) 7823], we have explored the absorption characteristics of several phosphine– and phosphite–IC 4 F 9 adducts by means of relativistic density functional theory and multireference configuration interaction methods. Based on the results of these computational and complementary experimental studies, we offer an explanation for the broad tailing of the absorption of t Bu 3 P-IC 4 F 9 and (MeO) 3 P-IC 4 F 9 into the visible-light region. Larger coordinate displacements of the ground and excited singlet potential energy wells in n Bu 3 P-IC 4 F 9 , in particular with regard to the P–I–C bending angle, reduce the Franck–Condon factors and thus the absorption probability compared to t Bu 3 P-IC 4 F 9 . Spectroscopic and computational evaluation of conformationally flexible and locked phosphites suggests that the reactivity of (MeO) 3 P may be the result of oxygen lone-pair participation and concomitant broadening of absorption. The proposed mechanism for the phosphine-catalyzed homolytic C–I cleavage of perfluorobutane iodide involves S1 ← S0 absorption of the adduct followed by intersystem crossing to the photochemically active T 1 state.
- Subjects
FRANCK-Condon principle; IODIDES; DENSITY functional theory; PHOSPHINES; FLUOROALKYL compounds; POTENTIAL energy
- Publication
Molecules, 2020, Vol 25, Issue 7, p1606
- ISSN
1420-3049
- Publication type
Article
- DOI
10.3390/molecules25071606