MOE Key Laboratory of Laser Life Science & Guangdong Provincial Key Laboratory of Laser Life Science, Guangzhou Key Laboratory of Spectral Analysis and Functional Probes, College of Biophotonics, South China Normal University, Guangzhou, 510631, China.
Phys Chem Chem Phys. 2022 Aug 17;24(32):19354-19361. doi: 10.1039/d2cp00904h.
Computational and condensed phase experimental evidence for the existence of S∴N and S∴O hemibonded structures has been reported previously, but no gas phase experimental evidence has been reported. To experimentally explore the existence of the S∴N and S∴O hemibonds in the gas phase, we recorded the infrared photodissociation action spectra of four cationic clusters: [CHSH-NH], [CHSCH-NH], [CHSCH-HO], and [CHOCH-HO]. Combined with the calculation results, it is found that the S∴N hemibonded structure is competitive with the S⋯HN H-bonded structure, though only the latter structure is actually observed in [CHSH-NH]. The spectral and theoretical results show that hemibonds can form between the second- (oxygen or nitrogen) and the third-period elements (sulfur) in the heterodimer clusters of [CHSCH-NH] and [CHSCH-HO]. However, the S∴N and S∴O hemibonded structures are found competitive with the C⋯HN and CH⋯O H-bonded structures, respectively, and both the structures coexist. On the other hand, the O∴O hemibonded structure is much less stable than other hydrogen bonded (H-bonded) structures in [CHOCH-HO], and it shows no clear contribution to the observed spectrum. This study provides direct spectroscopic evidence for the existence of S∴N and S∴O hemibonds in the gas phase and their competition with the H-bonds, which may be also fundamentally important in biological processes.
先前已有报道称，通过计算和凝聚相实验证据证实了 S∴N 和 S∴O 半键合结构的存在，但尚未有气相实验证据的报道。为了在气相中实验性地探索 S∴N 和 S∴O 半键的存在，我们记录了四个阳离子团簇的红外光解作用光谱：[CHSH-NH]、[CHSCH-NH]、[CHSCH-HO]和[CHOCH-HO]。结合计算结果发现，尽管[SCHSH-NH]中仅观察到 S⋯HN 氢键合结构，但 S∴N 半键合结构具有竞争性。光谱和理论结果表明，在[CHSCH-NH]和[CHSCH-HO]的杂二聚体簇中，第二周期（氧或氮）和第三周期元素（硫）之间可以形成半键。然而，S∴N 和 S∴O 半键合结构分别与 C⋯HN 和 CH⋯O H 键合结构具有竞争性，且这两种结构共存。另一方面，在[CHOCH-HO]中，O∴O 半键合结构比其他氢键合（H 键合）结构稳定得多，并且对观察到的光谱没有明显贡献。本研究为气相中 S∴N 和 S∴O 半键的存在及其与氢键的竞争提供了直接的光谱证据，这在生物过程中可能也具有重要的基础性意义。
