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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Sigma versus Pi Interactions in Alkali Metal Ion Binding to Azoles: Threshold Collision-Induced Dissociation and Ab Initio Theory Studies
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Sigma versus Pi Interactions in Alkali Metal Ion Binding to Azoles: Threshold Collision-Induced Dissociation and Ab Initio Theory Studies

机译：碱金属离子与唑的结合中的Sigma与Pi相互作用：阈值碰撞诱导的解离和从头算理论研究

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Threshold collision-induced dissociation of M~+(azole) with xenon is studied by guided ion beam mass spectrometry. M~+ include the following alkali metal ions: Li~+, Na~+, and K~+. The azoles studied include pyrrole, 1-methylpyrrole, pyrazole, 1-methylpyrazole, and 1-methylimidazole. In all cases, endothermic loss of the intact neural azole is observed as the primary reaction pathway. Minor production of M~+Xe formed by ligand exchange is also observed. The cross-section thresholds are interpreted to yield 0 and 298 K binding energies for M~+-azole after accounting for the effects of multiple ion-neutral collisions, internal energy of the reactant ions, and dissociation lifetimes. Ab initio calculations at MP2(full)/6-31G~* level of theory are used to determine the structures of these complexes and provide molecular constants necessary for the thermodynamic analysis of the experimental data. Single-point calculations at the MP2(full)/6-311+G(2d,2p) level using the MP2(full)/6-31G~* optimized geometries are used to obtain theoretical bond dissociation energies. Zero-point energy and basis set superposition error corrections are also included. Excellent agreement between theory and experiment is found for the Na~+ and K~+ systems, whereas the theoretical bond dissociation energies to the Li~+ systems are systematically lw. The calculated and measured bond dissociation energies are compared among the systems examined here and to previous values from the literature, to determine the influence that the metal ion, the nature of the binding interaction (π vs σ binding), and the dipole moment, quadrupole moment, and polarizability of the ligand have on the strength of the binding in these complexes.
机译：通过导向离子束质谱法研究了阈值碰撞诱导的M〜+（唑）与氙的离解。 M +包括以下碱金属离子：Li +，Na +和K +。研究的吡咯包括吡咯，1-甲基吡咯，吡唑，1-甲基吡唑和1-甲基咪唑。在所有情况下，观察到完整神经唑的吸热损失是主要的反应途径。还观察到通过配体交换形成的M〜+ Xe的生成量较小。在考虑了多次离子-中性碰撞，反应离子的内能和离解寿命的影响后，将横截面阈值解释为产生M〜+-唑的0和298 K结合能。理论上以MP2（full）/ 6-31G〜*的从头算计算来确定这些络合物的结构，并提供实验数据的热力学分析所需的分子常数。使用MP2（full）/ 6-31G〜*优化的几何结构在MP2（full）/ 6-311 + G（2d，2p）级别进行单点计算，以获得理论键解离能。还包括零点能量和基集叠加误差校正。对于Na〜+和K〜+体系，理论和实验之间发现了极好的一致性，而Li〜+体系的理论键解离能系统地降低了。将计算和测量的键解离能与此处检查的系统进行比较，并与文献中的先前值进行比较，以确定金属离子的影响，键相互作用的性质（πvsσ键）以及偶极矩，四极杆这些配体的结合强度和极化强度取决于结合强度。

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