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Quasistructural molecules
Wiley Interdisciplinary Reviews: Computational Molecular Science ( IF 16.8 ) Pub Date : 2019-07-24 , DOI: 10.1002/wcms.1432
Attila G. Császár 1, 2 , Csaba Fábri 1, 2 , János Sarka 3
Affiliation  

The concept of quasistructural molecules is introduced. For quasistructural molecules (a) the notion of a static equilibrium structure, corresponding to a minimum on the potential energy surface of the molecule, loses its strict meaning, (b) internal nuclear motions (rotations and vibrations) become dominant, resulting in an effective molecular structure often even qualitatively different from the equilibrium one, (c) separation of the internal nuclear motions breaks down, rotational and vibrational degrees of freedom cannot be separated from each other when interpreting even the lowest rovibrational eigenstates of the molecule, often resulting in effective rotational constants drastically different from the equilibrium ones even for the ground vibrational eigenstate, (d) classification of the rovibrational states requires the use of permutation‐inversion symmetry and molecular‐symmetry groups, and (e) some of the rovibrational eigenenergies assigned to a vibrational parent state exhibit unconventional (in the most striking cases “negative”) rotational contributions. Molecules showing quasistructural behavior include neutral species, such as dimethyl acetylene, charged species, such as urn:x-wiley:17590876:media:wcms1432:wcms1432-math-0001 and urn:x-wiley:17590876:media:wcms1432:wcms1432-math-0002, van der Waals complexes, such as CH4·H2O, and molecular complexes held together by halogen bonds, like CF3Cl·CH3F.

中文翻译:

准结构分子

介绍了准结构分子的概念。对于准结构分子(a)静态平衡结构的概念(相当于该分子的势能表面上的最小值)失去了严格的含义,(b)内部核运动(旋转和振动)占主导地位,从而产生了有效的平衡。分子结构通常甚至在质量上与平衡结构都不相同,(c)内部核运动的分离被破坏,即使在解释分子的最低旋转本征态时,旋转自由度和振动自由度也无法彼此分离,这通常导致有效的即使对于地面振动本征态,旋转常数也与平衡常数大不相同,(d)对振动状态的分类需要使用排列反转对称和分子对称组,并且(e)分配给振动母态的一些振动本征能量表现出非常规的(在最显着的情况下为“负”)旋转贡献。显示准结构行为的分子包括中性物质(例如二甲基乙炔)和带电物质(例如)骨灰盒:x-wiley:17590876:media:wcms1432:wcms1432-math-0001以及骨灰盒:x-wiley:17590876:media:wcms1432:wcms1432-math-0002诸如CH 4 ·H 2 O之类的范德华配合物,以及诸如CF 3 Cl·CH 3 F之类的通过卤素键结合在一起的分子配合物。
更新日期:2019-11-18
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