Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Mumbai, India.
J Phys Chem A. 2012 Dec 6;116(48):11965-72. doi: 10.1021/jp308735j. Epub 2012 Nov 26.
Structures, hydrogen bonding, and binding energies of H(4)SeA (A = O, S, Se) dimers and their cation radicals have been studied using DFT-B3LYP, MP2, and CCSD methods with 6-31++G(d,p), cc-pVTZ, and aug-cc-pVTZ basis sets. The binding energy (BE) order of the most stable neutral and cationic dimers have been found to be (H(2)Se···HOH) > (H(2)Se···HSH) > (H(2)Se···HSeH), and (H(2)Se···SeH(2))(+) > (H(2)Se···SH(2))(+) > (HSe···HOH(2))(+), respectively, by B3LYP/6-31++G(d,p) and MP2/aug-cc-pVTZ methods. Higher electronegativity of the heteroatom has been found to result in more stability of the neutral dimer but less of the cationic dimer. Among neutral dimers, structure with more electronegative heteroatom acting as proton donor has been found to be more stable. However, the hemibonded structure has been found to be more stable for the dimer cation radical unless the ionization potentials of the involved heteroatoms are very different, e.g., H(4)SeO(+). Vibrational frequency calculation suggests that an increase in electronegativity of A-atom results in a decrease in Se-H bond strength in H(4)SeA and H(4)SeA(+) dimers. The calculated values of Mulliken atomic charge/spin and hydrogen bond lengths of the dimers and their radical cations have also been discussed.
采用 DFT-B3LYP、MP2 和 CCSD 方法，结合 6-31++G(d,p)、cc-pVTZ 和 aug-cc-pVTZ 基组，研究了 H(4)SeA（A=O、S、Se）二聚体及其阳离子自由基的结构、氢键和结合能。通过 B3LYP/6-31++G(d,p)和 MP2/aug-cc-pVTZ 方法发现，最稳定的中性和阳离子二聚体的结合能（BE）顺序分别为（H(2)Se···HOH）＞（H(2)Se···HSH）＞（H(2)Se···HSeH）和（H(2)Se···SeH(2))(+)＞（H(2)Se···SH(2))(+)＞（HSe···HOH(2))(+)。杂原子的电负性越高，中性二聚体越稳定，但阳离子二聚体的稳定性越低。在中性二聚体中，具有较强电负性的杂原子作为质子供体的结构更为稳定。然而，对于二聚体阳离子自由基，除非涉及的杂原子的电离势差异非常大（例如 H(4)SeO(+)），否则半键合结构更为稳定。振动频率计算表明，A 原子的电负性增加会导致 H(4)SeA 和 H(4)SeA(+)二聚体中 Se-H 键强度降低。还讨论了二聚体及其自由基阳离子的 Mulliken 原子电荷/自旋和氢键长度的计算值。
