The two-dimensional shape information yielded by ion mobility-mass spectrometry (IM-MS), usually reported as collision cross section (CCS), is often correlated to the underlying three-dimensional structures of the ions through computational chemistry. Here, we used theoretical approaches based on molecular mechanics (MM), molecular dynamics (MD), and density functional theory (DFT) to elucidate the structures of sodiated poly(ethoxy phosphate) polymer ions at different degrees of polymerization (DP) for three different charge states (1+, 2+, and 3+) by comparing computational results to experimentally obtained CCS values. From the calculated structures, we extract several key interaction distances which merge in clusters for all screened charge states and DPs, independent of the three-dimensional structures and the polymer ion structural rearrangements. These distances were also used to extract the minimum coordination numbers in poly(ethoxy phosphate) and to describe the preferred coordination geometries. When sodiated and protonated polymer ions are compared, the experimental CCS evolutions differ at small DP values and merge at higher DPs. We investigated in more depth this difference for two selected species, namely, [PEtP5 + 2Na+]2+ and [PEtP5 + 2H+]2+. For the protonated ions, we explored the different protonation sites to extract three-dimensional structure candidates and rationalize the CCS behaviors.

中文翻译：

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离子淌度质谱研究气相中聚乙氧基磷酸酯链的钠配位和质子化

离子淌度质谱（IM-MS）产生的二维形状信息（通常报告为碰撞截面（CCS））通常通过计算化学与离子的基础三维结构相关。在这里，我们使用了基于分子力学（MM），分子动力学（MD）和密度泛函理论（DFT）的理论方法，阐明了三种聚合度（DP）下聚合的聚乙氧基磷酸酯聚合物离子的结构。通过将计算结果与实验获得的CCS值进行比较，可以得出不同的电荷状态（1 +，2 +和3+）。从计算出的结构中，我们提取出几个关键的相互作用距离，这些距离在所有筛选的电荷状态和DP的簇中合并，与三维结构和聚合物离子结构的重排无关。这些距离还用于提取聚（乙氧基磷酸酯）中的最小配位数并描述优选的配位数。当比较离子化和质子化的聚合物离子时，CCS的实验演变在较小的DP值时会有所不同，而在较高的DPs时会合并。我们更深入地研究了两个选定物种即[PEtP5 + 2Na +] 2+和[PEtP5 + 2H +] 2+的差异。对于质子化离子，我们探索了不同的质子化位点，以提取三维结构候选物并合理化CCS行为。当比较离子化和质子化的聚合物离子时，CCS的实验演变在较小的DP值下会有所不同，而在较高的DPs下会合并。我们更深入地研究了两个选定物种，即[PEtP5 + 2Na +] 2+和[PEtP5 + 2H +] 2+的差异。对于质子化离子，我们探索了不同的质子化位点，以提取三维结构候选物并合理化CCS行为。当比较离子化和质子化的聚合物离子时，CCS的实验演变在较小的DP值时会有所不同，而在较高的DPs时会合并。我们更深入地研究了两个选定物种即[PEtP5 + 2Na +] 2+和[PEtP5 + 2H +] 2+的差异。对于质子化离子，我们探索了不同的质子化位点，以提取三维结构候选物并合理化CCS行为。