Zhang Lijuan, Li Dazhi, Cheng Min, Du Yikui, Zhu Qihe
College of Chemistry and Chemical Engineering, Binzhou University, Binzhou, 256600, Shandong, PR China.
College of Chemistry and Chemical Engineering, Binzhou University, Binzhou, 256600, Shandong, PR China.
Spectrochim Acta A Mol Biomol Spectrosc. 2017 Aug 5;183:177-186. doi: 10.1016/j.saa.2017.04.023. Epub 2017 Apr 18.
The ab initio and dispersion-corrected density functional theory (DFT) calculations of the van der Waals (vdW) clusters of cis and trans 3-fluoro-N-methylaniline-Ar (3FNMA-Ar) (n=1,2) predict that, for cis and trans 3FNMA-Ar clusters, the π-bound geometry with the Ar atom sitting over the ring is the global minimum in both neutral and cationic states, while for cis and trans 3FNMA-Ar clusters, the [π|π]-bound sandwich structure with two Ar ligands occupying nearly equivalent π-bound positions above and below the ring plane is the global minimum. The vibronic spectra of cis and trans 3FNMA-Ar clusters in the S state were recorded by using one-color and two-color resonant two-photon ionization (R2PI) techniques, the comparison of which yields an estimate of the binding energy of cluster in the S state. It is found that the linear correlation between the redshift of the S←S electronic transition energy (E) of cluster and the E of the monomer also holds for the Ar clusters of hetero-di-substituted aromatics. By recording the photoionization efficiency (PIE) curves and mass-analyzed threshold ionization (MATI) dissociation spectra of cis and trans 3FNMA-Ar clusters, the ionization energies (IE) and binding energies of clusters in the D state are obtained. The MATI spectra of the cis and trans 3FNMA-Ar cations exhibit significant progressions of the vdW bending mode (b), indicating the structural changes of the clusters in the bending coordinate upon ionization. The combination of the three kinds of spectroscopic methods provides the binding energies of cis and trans 3FNMA-Ar clusters in the S, S and D states with good accuracy, and the values estimated by dispersion-corrected DFT calculations compare well with the experimental results. From our studies, the ωB97X-D and TD-ωB97X-D methods using high quality basis set are recommended for studying the intermolecular interaction of such vdW clusters in the ground and excited states.
对顺式和反式3-氟-N-甲基苯胺 - 氩（3FNMA - Ar）（n = 1,2）的范德华（vdW）团簇进行的从头算和色散校正密度泛函理论（DFT）计算预测，对于顺式和反式3FNMA - Ar团簇，Ar原子位于环上方的π键合几何结构在中性和阳离子状态下均为全局最小值，而对于顺式和反式3FNMA - Ar团簇，两个Ar配体分别占据环平面上方和下方几乎等效的π键合位置的[π|π]键合夹心结构为全局最小值。利用单色和双色共振双光子电离（R2PI）技术记录了顺式和反式3FNMA - Ar团簇在S态的振转光谱，通过比较可估算出团簇在S态的结合能。研究发现，团簇的S←S电子跃迁能量（E）的红移与单体的E之间的线性相关性对于杂二取代芳烃的Ar团簇也成立。通过记录顺式和反式3FNMA - Ar团簇的光电离效率（PIE）曲线和质量分析阈值电离（MATI）解离光谱，获得了团簇在D态的电离能（IE）和结合能。顺式和反式3FNMA - Ar阳离子的MATI光谱显示出vdW弯曲模式（b）的显著进展，表明电离时团簇在弯曲坐标上的结构变化。这三种光谱方法的结合以良好的精度提供了顺式和反式3FNMA - Ar团簇在S、S和D态的结合能，色散校正DFT计算估计的值与实验结果比较吻合。从我们的研究来看，建议使用高质量基组的ωB97X - D和TD - ωB97X - D方法来研究此类vdW团簇在基态和激发态的分子间相互作用。
