Moriyama Ryoichi, Sato Ryuki, Nakano Motoyoshi, Ohshimo Keijiro, Misaizu Fuminori
Department of Chemistry, Graduate School of Science, Tohoku University , 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
Institute for Excellence in Higher Education, Tohoku University , 41 Kawauchi, Aoba-ku, Sendai 980-8576, Japan.
J Phys Chem A. 2017 Aug 3;121(30):5605-5613. doi: 10.1021/acs.jpca.7b02431. Epub 2017 Jul 24.
Structural assignments of gas phase chromium oxide cluster anions, CrO (m = 1-7), have been achieved by comparison between experimental collision cross sections measured by ion mobility mass spectrometry and theoretical collision cross sections of optimized structures by quantum chemical calculations. In the mass spectrum, significant magic behavior between the numbers m and n was not observed for CrO, while wide ranges of compositions were observed around CrO to (CrO) as reported previously. The (CrO) (m = 3-7) ions were assigned to have monocyclic-ring structures for m = 3-5 and bicyclic rings for m = 6 and 7. In addition, gradual structural change from these cyclic structures of (CrO) to three-dimensional structures of CrO was found for m = 4-7. The energy levels of molecular orbitals of a calculated monocyclic structure of CrO were also found to be consistent with previous results of photoelectron spectroscopy, although those of the bicyclic isomer exhibited a different behavior. Moreover, the observation of abundant ions generated by collision induced dissociations at the inlet of the ion drift cell indicates that the larger sized (CrO) (m > 5) series were unstable and easily dissociated to smaller ions.
通过比较离子迁移质谱法测量的实验碰撞截面与量子化学计算优化结构的理论碰撞截面，实现了气相氧化铬团簇阴离子CrO（m = 1 - 7）的结构归属。在质谱图中，对于CrO，未观察到m和n数之间明显的幻数行为，而如先前报道的那样，在CrO到(CrO)周围观察到了广泛的组成范围。(CrO)（m = 3 - 7）离子被确定为m = 3 - 5时具有单环结构，m = 6和7时具有双环结构。此外，对于m = 4 - 7，发现从(CrO)的这些环状结构到CrO的三维结构存在逐渐的结构变化。虽然双环异构体的分子轨道能级表现出不同的行为，但计算得到的CrO单环结构的分子轨道能级也被发现与先前光电子能谱的结果一致。此外，在离子漂移池入口处碰撞诱导解离产生的大量离子的观察表明，较大尺寸的(CrO)（m > 5）系列不稳定，容易解离为较小的离子。
