Photofragmentation of the closo-Carboranes Part II: VUV Assisted Dehydrogenation in the closo-Carboranes and Semiconducting B10C2Hx Films

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• 作者：Eckart Rhl ; Norman F. Riehs ; Swayambhu Behera ; Justin Wilks ; Jing Liu ; H.-W. Jochims ; Anthony N. Caruso ; Neil M. Boag ; Jeffry A. Kelber ; Peter A. Dowben
• 刊名：Journal of Physical Chemistry A
• 出版年：2010
• 出版时间：July 15, 2010
• 年：2010
• 卷：114
• 期：27
• 页码：7284-7291
• 全文大小：472K
• 年卷期：v.114,no.27(July 15, 2010)
• ISSN：1520-5215

文摘

The dehydrogenation of semiconducting boron carbide (B₁₀C₂H_x) films as well as the three closo-carborane isomers of dicarbadodecaborane (C₂B₁₀H₁₂) and two isomers of the corresponding closo-phosphacarborane (PCB₁₀H₁₁) all appear to be very similar. Photoionization mass spectrometry studies at near-threshold gas phase photoionization indicate that the preferred pathway for dissociation of the parent cation species (C₂B₁₀H₁₀p>+p> or PCB₁₀H₉p>+p>) is, in all cases, the loss of H₂. Ab initio density functional theory (DFT) calculations indicate that energetically preferred sites for exopolyhedral hydrogen (B−H) bond dissociation are in all cases at B atoms opposite the C atoms in the parent cage molecule. The site of photodissociation of hydrogen from semiconducting boron carbide (B₁₀C₂H_x) films, fabricated by plasma-enhanced chemical vapor deposition, is a cage boron atom that can bond to nitrogen upon exposure to VUV light in the presence of NH₃. Shifts in core level binding energies due to nitrogen bond formation indicate that B−N bond formation occurs only at B atoms bound to other boron atoms (B−B sites) and not at B−C sites or at C sites, in agreement with gas phase results.