Qaisrani Muhammad Nawaz, Kumar Nandha, Dreßler Christian, Gebauer Ralph, Hassanali Ali
Ilmenau University of Technology, Theoretical Solid State Physics, Weimarer Straße 32, 98693 Ilmenau, Germany.
ICTP - The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy.
J Phys Chem Lett. 2025 Aug 21;16(33):8588-8595. doi: 10.1021/acs.jpclett.5c01499. Epub 2025 Aug 13.
Short hydrogen bonds, defined by donor-acceptor distances of less than 2.5 Å, represent a distinct regime in acid-base chemistry where conventional models of hydrogen bonding break down. In an organic crystal formed via a temperature-induced chemical transformation of l-glutamine, we previously identified a short hydrogen bond featuring a double-well potential indicative of an activated proton transfer. Here, using path-integral molecular dynamics, we show that nuclear quantum effects completely eliminate the classical barrier leading to a symmetrization of the proton along the hydrogen bond. Classically, proton transfer is strongly coupled to the rocking motion of a neighboring ammonium ion; under quantum effects, this coupling is significantly reduced. Furthermore, examination of the electronic structure through Wannier centers reveals a quantum-driven redistribution of bonding electrons, blurring the distinction between hydrogen bonding and covalency. Taken together, our findings indicate that nuclear quantum effects in this organic crystal create a regime in which the donor and acceptor simultaneously act as the acid and base.
由供体-受体距离小于2.5 Å定义的短氢键，代表了酸碱化学中的一种独特状态，在这种状态下，传统的氢键模型不再适用。在通过L-谷氨酰胺的温度诱导化学转变形成的有机晶体中，我们之前发现了一种具有双阱势的短氢键，这表明存在活化的质子转移。在此，我们使用路径积分分子动力学表明，核量子效应完全消除了经典势垒，导致质子沿氢键对称化。经典地，质子转移与相邻铵离子的摇摆运动强烈耦合；在量子效应下，这种耦合显著降低。此外，通过万尼尔中心对电子结构的研究揭示了键合电子的量子驱动重新分布，模糊了氢键和共价键之间的区别。综上所述，我们的研究结果表明，这种有机晶体中的核量子效应创造了一种供体和受体同时充当酸和碱的状态。
