Elliott Ben M, Koyle Eldon, Boldyrev Alexander I, Wang Xue-Bin, Wang Lai-Sheng
Department of Chemistry and Biochemistry, 0300 Old Main Hill, Utah State University, Logan, Utah 84322-0300, USA.
J Phys Chem A. 2005 Dec 22;109(50):11560-7. doi: 10.1021/jp054036v.
Gas-phase alkaline earth halide anions, MgX3(-) and CaX3(-) (X = Cl, Br), were produced using electrospray and investigated using photoelectron spectroscopy at 157 nm. Extremely high electron binding energies were observed for all species and their first vertical detachment energies were measured as 6.60 +/- 0.04 eV for MgCl3(-), 6.00 +/- 0.04 eV for MgBr3(-), 6.62 +/- 0.04 eV for CaCl3(-), and 6.10 +/- 0.04 eV for CaBr3(-). The high electron binding energies indicate these are very stable anions and they belong to a class of anions, called superhalogens. Theoretical calculations at several levels of theory were carried out on these species, as well as the analogous BeX3(-). Vertical detachment energy spectra were predicted to compare with the experimental observations, and good agreement was obtained for all species. The first adiabatic detachment energies were found to be substantially lower (by about 1 eV) than the corresponding vertical detachment energies for all the MX3(-) species, indicating extremely large geometry changes between MX3(-) and MX3. We found that all the MX3(-) anions possess D3h ((1)A1') structures and are extremely stable against dissociation into MX2 and X-. The corresponding neutral species MX3, however, were found to be only weakly bound with respect to dissociation toward MX2 + X. The global minimum structures of all the MX3 neutrals were found to be C2v ((2)B2), which can be described as (X2(-))(MX+) charge-transfer complexes, whereas the MX2...X (C2v, (2)B1) van der Waals complexes were shown to be low-lying isomers.
使用电喷雾法制备了气相碱土金属卤化物阴离子MgX₃⁻和CaX₃⁻（X = Cl、Br），并在157 nm下用光电子能谱对其进行了研究。观察到所有物种的电子结合能极高，其第一垂直脱附能测得如下：MgCl₃⁻为6.60±0.04 eV，MgBr₃⁻为6.00±0.04 eV，CaCl₃⁻为6.62±0.04 eV，CaBr₃⁻为6.10±0.04 eV。高电子结合能表明这些是非常稳定的阴离子，它们属于一类被称为超卤素的阴离子。对这些物种以及类似的BeX₃⁻进行了几个理论水平的理论计算。预测了垂直脱附能谱以与实验观察结果进行比较，并且所有物种都获得了良好的一致性。发现所有MX₃⁻物种的第一绝热脱附能比相应的垂直脱附能低得多（约1 eV），这表明MX₃⁻和MX₃之间存在极大的几何结构变化。我们发现所有MX₃⁻阴离子都具有D₃h（¹A₁'）结构，并且对于分解为MX₂和X⁻具有极高的稳定性。然而，发现相应的中性物种MX₃相对于分解为MX₂ + X仅弱结合。发现所有MX₃中性物种的全局最小结构为C₂v（²B₂），其可描述为（X₂⁻）（MX⁺）电荷转移络合物，而MX₂...X（C₂v，²B₁）范德华络合物被证明是低位异构体。
