Department of Chemistry, University of Utah, 315 S. 1400 E. Rm 2020, Salt Lake City, Utah 84112, USA.
J Phys Chem A. 2009 Dec 10;113(49):13742-51. doi: 10.1021/jp906241q.
In the preceding article, the hydration energies of Zn(2+)(H(2)O)(n) complexes, where n = 6-10, were measured using threshold collision-induced dissociation (CID) in a guided ion beam tandem mass spectrometer (GIBMS) coupled with an electrospray ionization (ESI) source. The present investigation explores the charge-separation processes observed, Zn(2+)(H(2)O)(n) --> ZnOH(+)(H(2)O)(m) + H(+)(H(2)O)(n-m-1), and the competition between this process and the loss of water. Our results demonstrate that charge-separation processes occur at variable complex sizes of n = 6, 7, and 8, prompting a redefinition of the critical size for charge separation. Experimental kinetic energy-dependent cross sections are analyzed to yield 0 K threshold energies for the charge-separation products and the effects of competition with this channel on the energies for losing one and two water ligands after accounting for multiple collisions, kinetic shifts, and energy distributions. A complete reaction coordinate is calculated for the n = 7 complex dissociating into ZnOH(+)(H(2)O)(3) + H(+)(H(2)O)(3). Calculated rate-limiting transition states for n = 6-8 are also compared to experimental threshold measurements for the charge-separation processes.
在上一篇文章中，使用与电喷雾电离（ESI）源耦合的引导离子束串联质谱仪（GIBMS）测量了 Zn(2+)(H(2)O)(n) 配合物（其中 n = 6-10）的水合能。本研究探讨了观察到的电荷分离过程，Zn(2+)(H(2)O)(n) --> ZnOH(+)(H(2)O)(m) + H(+)(H(2)O)(n-m-1)，以及该过程与失水之间的竞争。我们的结果表明，电荷分离过程发生在 n = 6、7 和 8 的可变配合物大小上，这促使对电荷分离的关键尺寸进行重新定义。分析实验动力学能量相关的截面，以获得电荷分离产物的 0 K 阈值能量，并考虑到多次碰撞、动力学位移和能量分布，该通道与失去一个和两个水配体的能量竞争的影响。计算了 n = 7 复合物解离为 ZnOH(+)(H(2)O)(3) + H(+)(H(2)O)(3)的完整反应坐标。还将 n = 6-8 的计算速率限制过渡态与实验电荷分离过程的阈值测量值进行了比较。
