Quantum chemical calculation of electron ionization mass spectra for general organic and inorganic molecules.
Quantum chemical calculation of electron ionization mass spectra for general organic and inorganic molecules.
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DOI：
10.1039/c7sc00601b
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发表时间：
2017-07-01
期刊：
影响因子：
8.4
通讯作者：
Grimme S
中科院分区：
文献类型：
--
作者：
Ásgeirsson V;Bauer CA;Grimme S
在QCEIMS程序中实现了一种新的紧密结合哈密顿量，允许在几小时内对元素Z = 86的系统进行基于第一性原理的EI质谱计算。我们介绍了一个完全独立版本的量子化学电子电离质谱（QCEIMS）程序[S]。Grimme Angew。化学。Int。原子序数高达Z = 86的元素组成的分子的有效模拟。最近开发的扩展紧密结合半经验方法GFN-xTB与QCEIMS相结合，从而消除了对第三方电子结构软件的依赖。此外，为了按照该方法的要求合理地计算电离势，本文还引入了第二种紧密结合变体IPEA-xTB。这种新颖的方法组合可以自动，快速和合理准确地计算元素周期表中结构不同分子的电子电离质谱。为了验证和检验该方法的可移植性，我们对一些具有代表性的有机，有机金属和主要无机系统进行了大规模模拟。23个分子的理论光谱直接与标准数据库中的实验数据进行了比较。首次提出了基于量子化学的有机金属体系，如二茂铁或乙酰丙酮铜的EI-MS。与以前使用的半经验方法相比，GFN-xTB更快，更健壮，并且总体上产生更高质量的光谱。部分分析的理论反应和碎裂机理在化学上是合理的，并以前所未有的细节揭示了高能气相离子化学的极端复杂性，包括解离前复杂的重排反应。
The implementation of a novel tight-binding Hamiltonian within the QCEIMS program allows the first-principles based computation of EI mass spectra within a few hours for systems containing elements up to Z = 86. We introduce a fully stand-alone version of the Quantum Chemistry Electron Ionization Mass Spectra (QCEIMS) program [S. Grimme, Angew. Chem. Int. Ed., 2013, 52, 6306] allowing efficient simulations for molecules composed of elements with atomic numbers up to Z = 86. The recently developed extended tight-binding semi-empirical method GFN-xTB has been combined with QCEIMS, thereby eliminating dependencies on third-party electronic structure software. Furthermore, for reasonable calculations of ionization potentials, as required by the method, a second tight-binding variant, IPEA-xTB, is introduced here. This novel combination of methods allows the automatic, fast and reasonably accurate computation of electron ionization mass spectra for structurally different molecules across the periodic table. In order to validate and inspect the transferability of the method, we perform large-scale simulations for some representative organic, organometallic, and main-group inorganic systems. Theoretical spectra for 23 molecules are compared directly to experimental data taken from standard databases. For the first time, realistic quantum chemistry based EI-MS for organometallic systems like ferrocene or copper(ii)acetylacetonate are presented. Compared to previously used semiempirical methods, GFN-xTB is faster, more robust, and yields overall higher quality spectra. The partially analysed theoretical reaction and fragmentation mechanisms are chemically reasonable and reveal in unprecedented detail the extreme complexity of high energy gas phase ion chemistry including complicated rearrangement reactions prior to dissociation.
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