化学计量的氧化钠团簇阳离子结构的离子迁移质谱法研究（英文）

Structures of Stoichiometric Sodium Oxide Cluster Cations Studied by Ion Mobility Mass Spectrometry

本文通过离子迁移质谱法研究了氧化钠团簇阳离子(NanOm+,n≤11)的稳定结构.质谱结果表明化学计量组成Na(Na2O)(n-1)/2^+(n=3、5、7、9和11)系列是稳定的,并且NaO(Na2O)(n-1)/2^+(n=5、7、9和11)系列作为二级稳定系列.为了获得这些团簇离子的结构,通过离子迁移率测量实验测定离子和氦缓冲气体之间的碰撞截面.同时计算了这些组合物优化结构的理论碰撞截面.结果表明,Na(Na2O)(n-1)/2^+和NaO(Na2O)(n-1)/2^+的结构除了n=9之外,其它具有相似结构框架. Na(Na2O)(n-1)/2^+所有的化合键位于钠和氧之间.另一方面,NaO(Na2O)(n-1)/2^+中除了Na-O键之外,还存在一个O-O氧键,表明NaO(Na2O)(n-1)/2^+具有过氧化物离子(O22-)作为Na(Na2O)(n-1)/2^+的氧化物离子(O2-)的替代物. Na(Na2O)(n-1)/2^+和NaO(Na2O)(n-1)/2^+两种稳定系列都是闭壳组合物.这些闭壳特征对氧化钠簇阳离子的稳定性具有强烈影响.

Structures of stable compositions of sodium oxide cluster cations (NanOm+,n≤11) have been investigated by ion mobility mass spectrometry. Stoichiometric compositions series, Na(Na2O)(n-1)/2^+(n=3, 5, 7, 9, and 11), were observed as stable composition series, and NaO(Na2O)(n-1)/2^+ series (n=5, 7, 9, and 11) were observed as secondary stable series in the mass spectra. To assign the structures of these cluster ion series, collision cross sections between the ions and helium buffer gas were determined experimentally from the ion mobility measurements. Theoretical collision cross sections were also calculated for optimized structures of these compositions. Finally, the structures of Na(Na2O)(n-1)/2^+ and NaO(Na2O)(n-1)/2^+ were assigned to those having similar structural frames for each n except for n=9. All bonds in the assigned structures of Na(Na2O)(n-1)/2^+ were between sodium and oxygen. On the other hand, there was one O-O bond in addition to Na-O bonds in NaO(Na2O)(n-1)/2^+. This result indicates that NaO(Na2O)(n-1)/2^+ have a peroxide ion (O22-) as a substitute for an oxide ion (O2-) of Na(Na2O)(n-1)/2^+. As a result, both stable series, Na(Na2O)(n-1)/2^+ and NaO(Na2O)(n-1)/2^+, are closed-shell compositions. These closed-shell characteristics have a strong influence on the stability of sodium oxide cluster cations.