Zhang Xiaoliu, Zhou Shengmin, Leonik Fedra M, Wang Lu, Kuroda Daniel G
Department of Chemistry, Louisiana State University Baton Rouge Louisiana 70803 USA
Department of Chemistry and Chemical Biology, Rutgers University Piscataway New Jersey 08854 USA
Chem Sci. 2022 May 19;13(23):6998-7006. doi: 10.1039/d2sc01784a. eCollection 2022 Jun 15.
Acid-base chemistry has immense importance for explaining and predicting the chemical products formed by an acid and a base when mixed together. However, the traditional chemistry theories used to describe acid-base reactions do not take into account the effect arising from the quantum mechanical nature of the acidic hydrogen shuttling potential and its dependence on the acid base distance. Here, infrared and NMR spectroscopies, in combination with first principles simulations, are performed to demonstrate that quantum mechanical effects, including electronic and nuclear quantum effects, play an essential role in defining the acid-base chemistry when 1-methylimidazole and acetic acid are mixed together. In particular, it is observed that the acid and the base interact to form a complex containing a strong hydrogen bond, in which the acidic hydrogen atom is neither close to the acid nor to the base, but delocalized between them. In addition, the delocalization of the acidic hydrogen atom in the complex leads to characteristic IR and NMR signatures. The presence of a hydrogen delocalized state in this simple system challenges the conventional knowledge of acid-base chemistry and opens up new avenues for designing materials in which specific properties produced by the hydrogen delocalized state can be harvested.
酸碱化学对于解释和预测酸和碱混合时形成的化学产物具有极其重要的意义。然而，用于描述酸碱反应的传统化学理论并未考虑酸性氢穿梭势的量子力学性质及其对酸碱距离的依赖性所产生的影响。在此，进行了红外光谱和核磁共振光谱，并结合第一性原理模拟，以证明当1-甲基咪唑和乙酸混合时，包括电子和核量子效应在内的量子力学效应在定义酸碱化学中起着至关重要的作用。特别地，可以观察到酸和碱相互作用形成一个包含强氢键的复合物，其中酸性氢原子既不靠近酸也不靠近碱，而是在它们之间离域。此外，复合物中酸性氢原子的离域导致了特征性的红外和核磁共振信号。这个简单系统中氢离域态的存在挑战了传统的酸碱化学知识，并为设计能够利用氢离域态产生的特定性质的材料开辟了新途径。
