Theoretical Study of Nascent Solvation in Ni+(Benzene)m, m = 3 and 4, Clusters

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• 作者：Miguel Castro ; Raul Flores ; Michael A. Duncan
• 刊名：Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：November 27, 2013
• 年：2013
• 卷：117
• 期：47
• 页码：12546-12559
• 全文大小：630K
• 年卷期：v.117,no.47(November 27, 2013)
• ISSN：1520-5215

文摘

The ligand versus solvent behavior of Ni⁺(C₆H₆)_3,4 complexes was studied using density functional theory all-electron calculations. Dispersion corrections were included with the BPW91-D2 method using the 6-311++G(2d,2p) basis set. The ground state (GS) for Ni⁺(C₆H₆)₃ has three benzene rings 3d鈭捪€ bonded to the metal. A two-layer isomer with two moieties coordinated 畏³鈥撐?sup>2 with Ni⁺, and the other one adsorbed by van der Waals interactions to the Ni⁺(C₆H₆)₂ subcluster, i.e., a 2 + 1 structure, is within about 8.4 kJ/mol of the GS. Structures with 3 + 1 and 2 + 2 ligand coordination were found for Ni⁺(C₆H₆)₄. The binding energies (D₀) of 28.9 and 26.0 kJ/mol for the external moieties of Ni⁺(C₆H₆)_3,4 are much smaller than that for Ni⁺(C₆H₆)₂, 193.0 kJ/mol, obtained also with BPW91-D2. This last D₀ overestimates somehow the experimental value, of 146.7 卤 11.6 kJ/mol, for Ni⁺(C₆H₆)₂. The abrupt fall for D₀(Ni⁺(C₆H₆)_3,4) shows that such molecules are bound externally as solvent species. These results agree with the D₀(Ni⁺(C₆H₆)₃) < 37.1 kJ/mol limit found experimentally for this kind of two-layer clusters. The ionization energies also decrease for m = 2, 3, and 4 (580.8, 573.1, and 558.6 kJ/mol). For Ni⁺(C₆H₆)_3,4, each solvent moiety bridges the benzenes of Ni⁺(C₆H₆)₂; their position and that of one internal ring mimics the tilted T-shape geometry of the benzene dimer (Bz₂). The distances from the center of the external to the center of the internal rings for m = 3 (4.686 脜) and m = 4 (4.523 脜) are shorter than that for Bz₂ (4.850 脜). This and charge transfer effects promote the (C^{未鈭?/sup>鈥揌未+)_int dipole鈭捪€_ext interactions in Ni+(C₆H₆)_3,4; 蟺鈥撓€ interactions also occur. The predicted IR spectra, having multiplet structure in the C鈥揌 region, provide insight into the experimental spectra of these ions.}