Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, c/Marcel·lí Domingo s/n, 43007, Tarragona, Spain.
Phys Chem Chem Phys. 2011 Dec 7;13(45):20136-45. doi: 10.1039/c1cp21209e. Epub 2011 Aug 24.
A complimentary combination of Density Functional Theory (DFT) methodology and Electrospray Ionization-Mass Spectrometry (ESI-MS) has been utilized to increase our limited understanding of the first nucleation steps in the formation of the XM(12)O(40) Keggin polyoxometalates (POMs) (where addenda metal atom M = W or Mo, and the heteroatom X = P or As). We postulate that the first key steps of nucleation into discrete, high nuclearity heteropolyanions proceed via the formation of isodinuclear species (e.g. M(2)O(7)), which undergo successive steps of protonation and water condensation to form a heterotrinuclear fragment, which acts as a template for the constituent parts required for subsequent aggregation and formation of the plenary Keggin heteropolyanion. The stability of calculated structures of the numerous postulated intermediates has been analysed and discussed in detail, and these results complemented using experimental mass spectrometry, using an assembly (reaction solution analysis) and disassembly (fragmentation of single crystals) approach. Overall, no significant differences between the Keggin POMs were found when changing the addenda metal atom (W or Mo) or the heteroatom (P or As); although small differences among the lowest-energy structures were detected.
密度泛函理论（DFT）方法和电喷雾电离-质谱（ESI-MS）的互补组合已被用于提高我们对XM(12)O(40) Keggin 多金属氧酸盐（POM）形成中最初成核步骤的有限理解（其中加合物金属原子 M = W 或 Mo，杂原子 X = P 或 As）。我们假设离散的、高核多阴离子成核的最初关键步骤是通过形成同双核物种（例如M(2)O(7)）进行的，这些物种经历连续的质子化和水缩合步骤，形成杂核三核片段，该片段充当随后聚合和形成完整 Keggin 杂多阴离子所需组成部分的模板。已详细分析和讨论了所提出的众多中间体的计算结构的稳定性，并使用实验质谱学（使用组装（反应溶液分析）和拆卸（单晶碎裂）方法）进行了补充。总体而言，改变加合物金属原子（W 或 Mo）或杂原子（P 或 As）时，Keggin POM 之间没有发现明显差异；尽管检测到最低能量结构之间的微小差异。
