Structures of Magnesium Oxide Cluster Cations Studied Using Ion Mobility Mass Spectrometry
Structures of Magnesium Oxide Cluster Cations Studied Using Ion Mobility Mass Spectrometry
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使用离子淌度质谱法研究氧化镁簇阳离子的结构
DOI：
10.1021/acs.jpca.9b08930
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
Misaizu Fuminori
中科院分区：
文献类型：
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作者：
Nakano Motoyoshi;Hebiguchi Daiki;Azuma Shohei;Moriyama Ryoichi;Ohshimo Keijiro;Misaizu Fuminori
通过比较离子迁移率质谱仪测量的实验碰撞截面和量子化学优化平衡结构的理论碰撞截面，对气相氧化镁团簇阳离子MgnOn+(n≤24)进行了结构归属。以岩盐和六角筒构造为基础的各种构造被指定为Forn=5-13和15。另一方面，只有岩盐型构造被指定为Forn=4、14、16-21和24。对于给定尺寸的六方管结构和岩盐结构，在小尺寸范围内(除4和14外，n≤为15)，CCS值和总能量接近。与岩盐结构相比，含≥16的团簇离子的六方管结构稳定性较差，CCSS较大。这些结果表明，随着团簇尺寸的增大，MgnOn+团簇的结构从岩盐和六方管结构的混合结构转变为纯岩盐结构。即使团簇尺寸增大，六角管结构中的所有原子都位于团簇的表面。相反，n=13、14和n≥17的岩盐结构在簇内有原子，这意味着岩盐结构的平均配位数比六角管结构的高得多。这种配位数的差异可归因于由混合结构向纯岩盐结构的转变。
Structural assignments of gas-phase magnesium oxide cluster cations, MgnOn+(n≤ 24), have been achieved from a comparison of experimental collision cross sections (CCSs) measured using ion mobility mass spectrometry and theoretical CCSs calculated for equilibrium structures optimized by quantum chemical calculations. Various structures based on rock-salt and hexagonal-tube structures were assigned forn= 5–13 and 15. On the other hand, only rock-salt type structures were assigned forn= 4, 14, 16–21, and 24. The CCS values and the total energies were close for the hexagonal-tube and rock-salt structures of a given size in the small size range (n≤ 15 except for 4 and 14). The hexagonal-tube structures of the cluster ions withn≥ 16 were less stable and had larger CCSs than the rock-salt structures. These results indicate that the structures of the MgnOn+clusters were changed from mixtures of rock-salt and hexagonal-tube structures to pure rock-salt structures with the growth of the cluster size. All atoms in the hexagonal-tube structures are located on the surface of the clusters, even if the cluster size increases. In contrast, the assigned rock-salt structures withn= 13, 14, andn≥ 17 had atoms inside the clusters, which means that the average coordination numbers are substantially higher for the rock-salt structures than for the hexagonal tube structures. The structural change from the mixed structures to pure rock-salt with an increase in sizencan be attributed to this difference in the coordination number.