Stephens Edward R, Dumlao Morphy, Xiao Dan, Zhang Daming, Donald William A
School of Chemistry, University of New South Wales, Sydney, NSW, 2052, Australia.
School of Electrical Engineering and Telecommunications, University of New South Wales, Sydney, NSW, 2052, Australia.
J Am Soc Mass Spectrom. 2015 Dec;26(12):2081-4. doi: 10.1007/s13361-015-1272-1. Epub 2015 Oct 5.
The extent of internal energy deposition upon ion formation by low temperature plasma and atmospheric pressure chemical ionization was investigated using novel benzylammonium thermometer ions. C-N heterolytic bond dissociation enthalpies of nine 4-substituted benzylammoniums were calculated using CAM-B3LYP/6-311++G(d,p), which was significantly more accurate than B3LYP/6-311++G(d,p), MP2/6-311++G(d,p), and CBS-QB3 for calculating the enthalpies of 20 heterolytic dissociation reactions that were used to benchmark theory. All 4-substituted benzylammonium thermometer ions fragmented by a single pathway with comparable dissociation entropies, except 4-nitrobenzylammonium. Overall, the extent of energy deposition into ions formed by low temperature plasma was significantly lower than those formed by atmospheric pressure chemical ionization under these conditions. Because benzylamines are volatile, this new suite of thermometer ions should be useful for investigating the extent of internal energy deposition during ion formation for a wide range of ionization methods, including plasma, spray and laser desorption-based techniques. Graphical Abstract ᅟ.
使用新型苄基铵温度计离子研究了低温等离子体和大气压化学电离形成离子时的内能沉积程度。使用CAM-B3LYP/6-311++G(d,p)计算了九种4-取代苄基铵的C-N异裂键解离焓，在计算用于基准理论的20个异裂解离反应的焓时，其比B3LYP/6-311++G(d,p)、MP2/6-311++G(d,p)和CBS-QB3显著更准确。除4-硝基苄基铵外，所有4-取代苄基铵温度计离子均通过单一途径裂解，具有可比的解离熵。总体而言，在这些条件下，低温等离子体形成的离子的能量沉积程度明显低于大气压化学电离形成的离子。由于苄胺具有挥发性，这套新的温度计离子应有助于研究包括等离子体、喷雾和基于激光解吸的技术在内的多种电离方法在离子形成过程中的内能沉积程度。图形摘要ᅟ。
