Double cation formation from the Photo-Fragmentation of the closo-Carboranes

Liu, J; Ruhl, E; Hitchcock, AP; McIlroy, DN; Bozek, JD; Tyliszczak, T; Knop-Gericke, A; Boag, NM; Dowben, PA

Abstract

Time-of-flight mass analysis with multi-stop coincidence detection has been used to study the multi-cation ionic fragmentation via fission of three isomeric carborane icosahedral cage compounds closo-1,2-orthocarborane, closo-1,7-metacarborane, closo-1,12-paracarborane (C2B10H12) following inner-shell excitation at or above the B is regime. Photoelectron-photoion-photoion coincidence (PEPIPICO) spectroscopy was used to study the dominant fission routes in the core level excitation regime. Series of ion pairs are identified, where asymmetric fission dominates, leading to ion pairs of different mass. The fragmentation yields and charge separation mass spectra of all three isomers are generally quite similar in that the ion pairs (H+, Y+), Y-11(+)), and (Y-3(+), Y-9(+)) dominate, where denotes the mass region from B+ to CH. Slight differences are observed at the B 1s-threshold, where the H+ and BH2+/CH+ ion pairs dominate for ortho-and metacarborane, while (Y+, Y-11(+)) ion pairs dominate the multi-photofragment ion yield of paracarborane. These similarities and distinct differences in charge separation are discussed by considering the energetics of these three major species of ion pairs, as well as charge distributions in closo-carboranes and charge distributions in the carborane cage. It is shown that product formation via charge separation is driven by electronic relaxation, so that the lowest energy products are not necessarily formed.

• Journal Article Type: Article
• Acceptance Date: Jan 10, 2014
• Publication Date: May 1, 2014
• Deposit Date: Jun 17, 2015
• Journal: Zeitschrift fur Physikalische Chemie
• Print ISSN: 0942-9352
• Publisher: De Gruyter
• Peer Reviewed: Peer Reviewed
• Volume: 228
• Issue: 4-5
• Pages: 421-436
• DOI: https://doi.org/10.1515/zpch-2014-0447
• Publisher URL: http://dx.doi.org/10.1515/zpch-2014-0447
• Related Public URLs: http://www.degruyter.com/view/j/zpch
• Additional Information: Funders : Defense Threat Reduction Agency;Deutsche Forschungsgemeinschaft;National Aeronautics and Space Administration;Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division of the US Department of Energy;Fonds der Chemischen Industrie