Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, Chicago, IL 60637, USA.
Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, GA 30322, USA.
Science. 2021 Jan 8;371(6525):160-164. doi: 10.1126/science.abe1951.
Hydrogen bonds (H-bonds) can be interpreted as a classical electrostatic interaction or as a covalent chemical bond if the interaction is strong enough. As a result, short strong H-bonds exist at an intersection between qualitatively different bonding descriptions, with few experimental methods to understand this dichotomy. The [F-H-F] ion represents a bare short H-bond, whose distinctive vibrational potential in water is revealed with femtosecond two-dimensional infrared spectroscopy. It shows the superharmonic behavior of the proton motion, which is strongly coupled to the donor-acceptor stretching and disappears on H-bond bending. In combination with high-level quantum-chemical calculations, we demonstrate a distinct crossover in spectroscopic properties from conventional to short strong H-bonds, which identify where hydrogen bonding ends and chemical bonding begins.
氢键 (H-bonds) 可以被解释为经典的静电相互作用，或者如果相互作用足够强，也可以被解释为共价化学键。因此，在定性不同的键合描述的交点处存在短而强的 H 键，很少有实验方法可以理解这种二分法。[F-H-F]离子代表裸露的短氢键，其在水中独特的振动势能可以通过飞秒二维红外光谱来揭示。它显示了质子运动的超谐行为，质子运动与供体-受体伸缩强烈耦合，并在 H 键弯曲时消失。结合高精度量子化学计算，我们证明了从常规到短而强 H 键的光谱性质的明显转变，这确定了氢键结束和化学键开始的位置。
