Graphical Transition Moment Decomposition and Conceptual Density Functional Theory Approaches to Study the Fundamental and Lower-Level Overtone Absorption Intensities of Some OH Stretching Vibrations
Graphical Transition Moment Decomposition and Conceptual Density Functional Theory Approaches to Study the Fundamental and Lower-Level Overtone Absorption Intensities of Some OH Stretching Vibrations
复制标题
图解跃迁矩分解和概念密度泛函理论方法研究某些 OH 伸缩振动的基本和低级泛音吸收强度
DOI：
10.1021/acs.jpca.0c11619
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Yabushita Satoshi
中科院分区：
文献类型：
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作者：
Tsuyuki Masafumi;Furudate Shunki;Kugaya Yuto;Yabushita Satoshi
由分子结构变化引起的电子密度迁移的研究在化学的各个领域都是至关重要的。为了解决这个问题的一般和研究振动的吸收强度，我们分析敏感的偶极矩函数（DMF）的分子相结合的线性响应函数的概念DFT和键偶极子分离的量子理论的原子在分子中的图形过渡时刻分解方案。OH伸缩振动的基本强度强烈地依赖于取代基，但仅弱地依赖于分子构象。有趣的是，在一些醇中，已经观察到完全相反的趋势，为较低水平的泛音强度：弱的取代基依赖性，但较强的构象依赖性。众所周知，氢键复合物的形成增加了OH伸缩基本强度，但不太为人所知的是它们的泛音强度的降低。为了更全面地研究这些特性，我们采用DFT方法，在OH伸缩坐标Δ R的局域模模型下，计算了乙醇、三氟乙醇（TFE）和氢键苯酚（PhOH）体系的构象异构体的强度（Δ v = 1，2，3）.计算了它们的电子密度对Δ R的一阶和二阶导数，并利用它们的键矩进行了解释.对于乙醇和TFE，OH，CC和CH键矩被发现作出重要贡献的分子DMF衍生物平行的OH键。OH键仅对DMF的一阶导数有贡献，其构象依赖性由每个结构的电荷极化的大小决定。在CC键区域的电子密度衍生物在很大程度上保持在内部旋转，因此，它们的构象依赖的贡献表示的CC键方向的几何因子。CH键的OH键的反周面位置被发现作出了显着的贡献，DMF的二阶衍生物中的gauche构象。取代基上的电子密度迁移的重要性也被确定在氢键苯酚，其中芳香环上的π-电子密度的变化被清楚地显示。这种迁移产生了垂直和平行于OH键的DMF衍生物，并强烈影响吸收强度。在所有的情况下，一些取代基上的键矩有助于第一和第二DMF衍生物的结构依赖性的方式，从而解释了它们的立体电子效应。
The investigation of electron density migrations caused by molecular structure changes is of central importance in various fields of chemistry. To address this topic in general and to study absorption intensities of vibrations, we analyze sensitive dipole moment functions (DMFs) of a molecule by combining the linear response function of conceptual DFT and bond dipoles separated by the quantum theory of atoms in molecules with a graphical transition moment decomposition scheme. The fundamental intensities of OH stretching vibrations depend strongly on the substituents but only weakly on the molecular conformations. Interestingly, in some alcohols, completely opposite trends have been observed for the lower-level overtone intensities: a weak substituent dependence but a stronger conformation dependence. It is well known that the formation of a hydrogen-bonded complex increases the OH stretching fundamental intensity, but less well known is the decrease in their overtone intensities. To investigate these characteristics comprehensively, we calculated their intensities (Δv= 1, 2, and 3) for conformers of ethanol and trifluoroethanol (TFE) and hydrogen-bonded phenol (PhOH) systems via the DFT method in the local mode model for the OH stretching coordinate ΔR. Their first and second derivatives of the electron density with respect to ΔRwere calculated and interpreted using their bond moments. For ethanol and TFE, the OH, CC, and CH bond moments were found to make an important contribution to the molecular DMF derivatives parallel to the OH bond. The OH bond contributes only to the first derivative of DMF, and its conformational dependence is determined by the magnitude of the charge polarization of each structure. The electron density derivatives in the CC bond region were largely maintained during the internal rotation; thus, their conformation-dependent contributions were expressed by a geometrical factor of the CC bond direction. The CH bond at the antiperiplanar position of the OH bond was found to make a remarkably large contribution to the second derivative of DMF in the gauche conformer. The importance of electron density migration on substituents was also identified in the hydrogen-bonded phenol, in which the π-electron density change on the aromatic ring was clearly shown. This migration creates the DMF derivatives both perpendicular and parallel to the OH bond and strongly affects the absorption intensities. In all the cases, some bond moments on the substituents contribute to the first and second DMF derivatives in a structure-dependent manner, thus explaining their stereoelectronic effects.