Valadbeigi Younes, Azizmohammadi Sima, Ilbeigi Vahideh
Department of Chemistry, Faculty of Science, Imam Khomeini International University, Qazvin, Iran.
TOF Tech. Pars Company, Isfahan Science & Technology Town, Isfahan, Iran.
J Phys Chem A. 2020 Apr 30;124(17):3386-3397. doi: 10.1021/acs.jpca.0c00118. Epub 2020 Apr 16.
The ionization of tartaric acid (TA) in an atmospheric pressure chemical ionization corona discharge ion source was studied by ion mobility spectrometry (IMS) with zero air as the drift gas. Density functional theory was used for structural and thermodynamic analyses of the produced ionic clusters. Ion mobility spectra of TA were recorded in both positive and negative modes of CD with and without ammonia and chloroform as dopants in order to produce NH and Cl, respectively, as the reactant ions (RIs). In the absence of these dopants, the RIs were mainly HO and O in the positive and negative CD, respectively. TA solutions in water and methanol were injected into the ionization region of the IMS instrument, and the product cations TA·H(HO), TA·H(CHOH), TA·NH, and TA·NH(CHOH) were observed in the positive CD. Anionic clusters (TA-H), (TA-H)·CHOH, (TA-H)·TA, TA·Cl, and (TA)Cl were produced in the negative CD. The anions TA·Cl and (TA)Cl were not produced in an air atmosphere, and we observed their peaks when pure oxygen was used as the drift gas. Optimized structures of the clusters showed that TA·NH, TA·Cl, and (TA)Cl are small host-guest systems in the gas phase, with TA as a host. (TA)Cl is a weakly bonded complex (an anion-bound dimer) that was observed at atmospheric pressure. The proton-bound dimer TA·H·TA was not produced in the positive CD, while the anionic dimer (TA-H)·TA was observed in the negative CD. This phenomenon was interpreted on the basis of the hydration of TA·H and (TA-H).
采用离子迁移谱（IMS），以零空气作为漂移气体，研究了酒石酸（TA）在大气压化学电离电晕放电离子源中的电离情况。利用密度泛函理论对所产生的离子簇进行结构和热力学分析。在有和没有氨及氯仿作为掺杂剂的情况下，分别以产生NH⁺和Cl⁻作为反应离子（RIs），记录了TA在电晕放电（CD）正、负模式下的离子迁移谱。在没有这些掺杂剂时，正、负CD中的RIs分别主要是H₃O⁺和O⁻。将水和甲醇中的TA溶液注入IMS仪器的电离区域，在正CD中观察到产物阳离子TA·H⁺(H₂O)、TA·H⁺(CH₃OH)、TA·NH₄⁺和TA·NH₄⁺(CH₃OH)。在负CD中产生阴离子簇(TA-H⁻)、(TA-H⁻)·CH₃OH、(TA-H⁻)·TA、TA·Cl⁻和(TA)Cl⁻。阴离子TA·Cl⁻和(TA)Cl⁻在空气气氛中不产生，当使用纯氧作为漂移气体时我们观察到了它们的峰。簇的优化结构表明，TA·NH₄⁺、TA·Cl⁻和(TA)Cl⁻是气相中的小主体-客体体系，以TA作为主体。(TA)Cl⁻是一种在大气压下观察到的弱键合络合物（阴离子结合二聚体）。质子结合二聚体TA·H⁺·TA在正CD中未产生，而阴离子二聚体(TA-H⁻)·TA在负CD中被观察到。基于TA·H⁺和(TA-H⁻)的水合作用对这一现象进行了解释。
