Wu Jenna W J, Moriyama Ryoichi, 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.
Phys Chem Chem Phys. 2017 Sep 20;19(36):24903-24914. doi: 10.1039/c7cp04017b.
Herein, the compositions and geometrical structures of niobium oxide cluster ions were studied and compared with those of the lighter Group 5 counterpart vanadium oxide cluster ions by ion-mobility mass spectrometry (IM-MS). As a result of collision-induced dissociation in IM-MS, the compositions were found to be dependent on an odd and even number of niobium atoms, whereby the ions with (NbO)(NbO) and (NbO)(NbO) were identified as stable compositions for an odd number of Nb atoms, whereas (NbO) and (NbO)(NbO) were identified as stable compositions for an even number of Nb atom clusters. Furthermore, structural transitions were observed between m = 8 and 9 for cluster cations and m = 7 and 8 for cluster anions for experimental collision cross-sections (CCSs), which were determined from the arrival times in the ion-mobility measurements. Quantum chemical calculations were conducted on several structural candidates of these compositions for m = 2-12. For cluster cations with the sizes between m = 2 and 8 and cluster anions with m = 2-7, the structures were found to be similar to those of vanadium oxide cluster ions upon comparing the experimental CCSs with the theoretical CCSs of optimized structures. As compared to the vanadium oxide cluster ions, niobium oxide cluster cations with m ≥ 9 and anions with m ≥ 8 consisted of structures where some niobium atoms had more than five oxygen-atom coordination; thus, compact structures could be achieved in the case of niobium oxide cluster ions.
在此，通过离子淌度质谱法（IM-MS）研究了氧化铌簇离子的组成和几何结构，并与较轻的第5族对应物氧化钒簇离子的组成和几何结构进行了比较。在IM-MS中的碰撞诱导解离结果表明，组成取决于铌原子的奇数和偶数，由此，具有（NbO）（NbO）和（NbO）（NbO）的离子被确定为奇数个铌原子的稳定组成，而（NbO）和（NbO）（NbO）被确定为偶数个铌原子簇的稳定组成。此外，对于簇阳离子，在m = 8和9之间观察到结构转变，对于簇阴离子，在m = 7和8之间观察到结构转变，这是根据离子淌度测量中的到达时间确定的实验碰撞截面（CCS）。对这些组成的几种结构候选物进行了m = 2-12的量子化学计算。对于尺寸在m = 2和8之间的簇阳离子以及m = 2-7的簇阴离子，将实验CCS与优化结构的理论CCS进行比较时，发现其结构与氧化钒簇离子的结构相似。与氧化钒簇离子相比，m≥9的氧化铌簇阳离子和m≥8的阴离子由一些铌原子具有超过五个氧原子配位的结构组成；因此，氧化铌簇离子可以实现紧凑结构。
