Structural Determination of a Transient Isomer of CH{sub 2}I{sub 2} by Picosecond X-Ray Diffraction

• Published in: Physical review letters Vol. 94; no. 24
• Main Authors: Davidsson, Jan, Georgiou, Panayiotis, Poulsen, Jens, Department of Chemistry, Goeteborg Univeristy, Box SE 412 96 Gothenburg, Cammarata, Marco, Wouts, Remco, Katona, Gergely, Jacobson, Frida, Neutze, Richard, Plech, Anton, European Synchrotron Radiation Facility, Grenoble Cedex 38043, BP 220, Wulff, Michael, Nyman, Gunnar
• Format: Journal Article
• Language: English
• Published: United States 24-06-2005
• Subjects: ATOMS; CHEMICAL REACTIONS; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COVALENCE; ELECTRON DIFFRACTION; IODINE; ISOMERS; MOLECULES; ORGANIC COMPOUNDS; PHOTOCHEMISTRY; RADICALS; RECOMBINATION; SOLUTIONS; SOLVENTS; SPECTRA; STRUCTURAL MODELS; TIME RESOLUTION; X-RAY DIFFRACTION
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.94.245503

Ultrafast time-resolved spectroscopic studies of complex chemical reactions in solution are frequently hindered by difficulties in recovering accurate structural models for transient photochemical species. Time-resolved x-ray and electron diffraction have recently emerged as techniques for probing the structural dynamics of short lived photointermediates. Here we determine the structure of a transient isomer of photoexcited CH{sub 2}I{sub 2} in solution and observe the downstream reactions of the initial photoproducts. Our results illustrate how geminate recombination proceeds via the formation of a transient covalent bond onto the iodine atom remaining with the parent molecule. Further intramolecular rearrangements are thus required for the CH{sub 2}I-I isomer to return to CH{sub 2}I{sub 2}. The generation of I{sub 3}{sup -} from those iodine radicals escaping the solvent cage is also followed with time.