Indelicato Serena, Bongiorno David, Turco Liveri Vincenzo, Mele Andrea, Panzeri Walter, Castiglione Francesca, Ceraulo Leopoldo
Department STEBICEF, University of Palermo, Via Archirafi n.32, I-90123, Palermo, Italy; CGA-UniNetLab, University of Palermo, Via F. Marini n.14, I-90128, Palermo, Italy.
Rapid Commun Mass Spectrom. 2014 Dec 15;28(23):2523-30. doi: 10.1002/rcm.7045.
The study of surfactant organization in vacuum allows surfactant-surfactant interaction to be unveiled in the absence of surrounding solvent molecules. Knowledge on their chemical-physical properties may also lead to the definition of more efficient gas-phase carriers, air-cleaning agents and nanoreactors. In addition, the presence of lanthanide-group ions adds unique photochemical properties to surfactants.
The structural features, stability and fragmentation patterns of charged aggregates formed by lanthanide-functionalized surfactants, ytterbium and erbium bis(2-ethylhexyl)sulfosuccinate ((AOT)3Yb and (AOT)3Er), have been investigated by electrospray ionization mass spectrometry (ESI-MS), tandem mass spectrometry (ESI-MS/MS) and energy-resolved mass spectrometry (ER-MS).
The experimental data indicate that the self-assembling of (AOT)3Yb and (AOT)3Er in the gas phase leads to the formation of a wide range of singly charged aggregates differing in their aggregation number, relative abundance and stability. In addition to specific effects on aggregate organization due to the presence of lanthanide ions, ER-MS experiments show rearrangements and in-cage reactions activated by collision, eventually including alkyl chain intra-cluster migration.
Analysis of the experimental findings suggests that the observed chemical transformations occur within an organized supramolecular assembly rather than in a random association of components. The fragmentation pathways leading to the neutral loss of a fragment of nominal mass 534 Da, assigned as C28 H54 O7 S, from some positively charged aggregates has been rationalized.
在真空中研究表面活性剂的组织形式能够在没有周围溶剂分子的情况下揭示表面活性剂 - 表面活性剂之间的相互作用。了解它们的化学物理性质也可能有助于定义更高效的气相载体、空气清洁剂和纳米反应器。此外，镧系元素离子的存在赋予了表面活性剂独特的光化学性质。
通过电喷雾电离质谱（ESI-MS）、串联质谱（ESI-MS/MS）和能量分辨质谱（ER-MS）研究了镧系元素功能化表面活性剂双（2-乙基己基）磺基琥珀酸镱和双（2-乙基己基）磺基琥珀酸铒（（AOT）3Yb和（AOT）3Er）形成的带电聚集体的结构特征、稳定性和碎片化模式。
实验数据表明，（AOT）3Yb和（AOT）3Er在气相中的自组装导致形成了一系列单电荷聚集体，它们在聚集数、相对丰度和稳定性方面存在差异。除了镧系离子的存在对聚集体组织产生的特定影响外，ER-MS实验还显示了由碰撞激活的重排和笼内反应，最终包括烷基链簇内迁移。
对实验结果的分析表明，观察到的化学转化发生在有组织的超分子组装体内，而不是在组分的随机缔合中。已经对一些带正电荷的聚集体中导致标称质量为534 Da（指定为C28 H54 O7 S）的片段中性损失的碎片化途径进行了合理分析。
