Magos-Palasyuk Ewelina, Litwiniuk Aleksander, Palasyuk Taras
Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224, Warsaw, Poland.
Faculty of Mathematics and Natural Sciences, Cardinal Stefan Wyszynski University in Warsaw, Woycickiego 1/3, 01-938, Warsaw, Poland.
Sci Rep. 2020 Oct 15;10(1):17431. doi: 10.1038/s41598-020-74654-0.
In situ high-pressure synchrotron X-ray diffraction, Raman scattering, and complementary first-principles calculations have revealed that structural and spectroscopic properties of lithium amidoborane compound are largely determined by multiple heteropolar dihydrogen bonds. The crystal structure of the compound is stabilized by dimeric complexes, wherein molecular ions bind together by intermolecular dihydrogen bonds of unconventional type. This strong intermolecular coupling determines stable character of the crystal structure in the pressure range up to ~ 30 GPa and is spectroscopically manifested by pronounced changes related to molecular vibrations of the amino group: the splitting of stretching modes, the anomalous behavior of wagging modes as well as Fermi resonance due to vibrational coupling of bending and stretching modes, significantly enhanced above 10 GPa. Unconventional nature of dihydrogen bonds is confirmed by the frequency increase, blueshift, of NH stretching modes with pressure. A role of certain hydrogen mediated interactions in the process of dehydrogenation of ammonia borane and its alkali metal derivatives is speculated. Findings presented here call for reconsideration of hydrogen release mechanism from alkali metal ammonia borane derivatives. The work makes significant contribution towards establishing the general theory of ubiquitous and versatile hydrogen mediated interactions.
原位高压同步辐射X射线衍射、拉曼散射以及互补的第一性原理计算表明，氨基硼氢化锂化合物的结构和光谱性质在很大程度上由多个异极双氢键决定。该化合物的晶体结构通过二聚体配合物得以稳定，其中分子离子通过非常规类型的分子间双氢键结合在一起。这种强分子间耦合决定了晶体结构在高达约30 GPa的压力范围内的稳定性，并且在光谱上表现为与氨基分子振动相关的显著变化：伸缩模式的分裂、摇摆模式的异常行为以及由于弯曲和伸缩模式的振动耦合导致的费米共振，在10 GPa以上显著增强。双氢键的非常规性质通过NH伸缩模式随压力的频率增加（蓝移）得到证实。推测了某些氢介导的相互作用在氨硼烷及其碱金属衍生物脱氢过程中的作用。此处呈现的研究结果呼吁重新考虑碱金属氨硼烷衍生物的氢释放机制。这项工作为建立普遍存在且通用的氢介导相互作用的一般理论做出了重大贡献。
