Laser Desorption Mass Spectrometry of End Group-Protected Linear Polyynes: Evidence of Laser-Induced Cross-Linking

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• 作者：Rolf W. Kirschbaum ; Dominik Prenzel ; Stephanie Frankenberger ; Rik R. Tykwinski ; Thomas Drewello
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：February 5, 2015
• 年：2015
• 卷：119
• 期：5
• 页码：2861-2870
• 全文大小：577K
• ISSN：1932-7455

文摘

End group-protected linear polyynes of composition Tr*鈥?C鈮)_n鈥揟r* (with Tr* representing the super trityl group and n = 2, 4, 6, 8, 10) and tBu鈥?C鈮)₆鈥?i>tBu (with tBu being the tertiary butyl group) have been studied by laser desorption ionization (LDI) time-of-flight (ToF) mass spectrometry. tBu-terminated polyyne molecules show considerably higher stability during laser activation than Tr*-end-capped polyyne molecules. A key feature is the abundant formation of oligomeric species upon laser activation. Tandem mass spectrometry reveals strong bonding within the oligomers which indicates cross-linking of the former polyynes within the oligomers. The process is more abundantly occurring and less energy demanding than the laser-induced coalescence of C₆₀. Cross-linking is more efficient with the smaller end group (tBu), and larger oligomers are formed when the chain length of the polyyne increases, both a result of enhanced interaction of the triple bonds in neighboring chains. The presence of the matrix molecules in matrix-assisted (MA)LDI hinders the polyyne interaction, and oligomer formation is markedly reduced.