Ma Lifu, Koka Joseph, Stace Anthony J, Cox Hazel
Department of Physical and Theoretical Chemistry, School of Chemistry, University of Nottingham , University Park, Nottingham NG7 2RD, United Kingdom.
J Phys Chem A. 2014 Nov 13;118(45):10730-7. doi: 10.1021/jp506530g. Epub 2014 Nov 3.
Photofragmentation with tunable UV radiation has been used to generate a spectrum for the copper-bis(benzene) complex, Cu(C6H6)2, in the gas phase. The ions were held in an ion trap where their temperature was reduced to ∼150 K, whereby the spectrum revealed two broad features at ∼38,200 and ∼45,700 cm(-1). Detailed calculations using density functional theory (DFT) show the complex can occupy three minimum energy structures with C2v and C2 (staggered and eclipsed) symmetries. Adiabatic time-dependent DFT (TDDFT) has been used to identify electronic transitions in Cu(benzene)2, and the calculations show these to fall into two groups that are in excellent agreement with the experimental data. However, the open-shell electronic configuration of Cu(2+) (d(9)) may give rise to excited states with double-excitation character, and the single-excitation adiabatic TDDFT treatment leads to extensive spin contamination. By quantifying the extent of spin contamination and allowing for the inclusion of a small percentage (∼10%), the theory can provide quantitative agreement with the experimental data.
利用可调谐紫外辐射进行光解离已用于在气相中生成双（苯）铜配合物Cu(C₆H₆)₂的光谱。离子被捕获在离子阱中，其温度降至约150 K，在此条件下光谱显示在约38200和约45700 cm⁻¹处有两个宽峰。使用密度泛函理论（DFT）进行的详细计算表明，该配合物可以占据具有C₂ᵥ和C₂（交错和重叠）对称性的三种最低能量结构。绝热含时密度泛函理论（TDDFT）已用于识别Cu(苯)₂中的电子跃迁，计算结果表明这些跃迁可分为两组，与实验数据非常吻合。然而，Cu(2+)（d⁹）的开壳层电子构型可能会产生具有双激发特征的激发态，单激发绝热TDDFT处理会导致大量的自旋污染。通过量化自旋污染的程度并允许包含小百分比（约10%），该理论可以与实验数据达成定量一致。
