Kasalova Veronika, Allen Wesley D, Schaefer Henry F, Pillai E Dinesh, Duncan Michael A
Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602-2525, USA.
J Phys Chem A. 2007 Aug 9;111(31):7599-610. doi: 10.1021/jp071206q. Epub 2007 May 19.
In support of mass-selected infrared photodissociation (IRPD) spectroscopy experiments, coupled-cluster methods including all single and double excitations (CCSD) and a perturbative contribution from connected triple excitations [CCSD(T)] have been used to study the V+(H2O) and ArV+(H2O) complexes. Equilibrium geometries, harmonic vibrational frequencies, and dissociation energies were computed for the four lowest-lying quintet states (5A1, 5A2, 5B1, and 5B2), all of which appear within a 6 kcal mol(-1) energy range. Moreover, anharmonic vibrational analyses with complete quartic force fields were executed for the 5A1 states of V+(H2O) and ArV+(H2O). Two different basis sets were used: a Wachters+f V[8s6p4d1f] basis with triple-zeta plus polarization (TZP) for O, H, and Ar; and an Ahlrichs QZVPP V[11s6p5d3f2g] and Ar[9s6p4d2f1g] basis with aug-cc-pVQZ for O and H. The ground state is predicted to be 5A1 for V+(H2O), but argon tagging changes the lowest-lying state to 5B1 for ArV+(H2O). Our computations show an opening of 2 degrees -3 degrees in the equilibrium bond angle of H2O due to its interaction with the metal ion. Zero-point vibrational averaging increases the effective bond angle further by 2.0 degrees -2.5 degrees, mostly because of off-axis motion of the heavy vanadium atom rather than changes in the water bending potential. The total theoretical shift in the bond angle of about +4 degrees is significantly less than the widening near 9 degrees deduced from IRPD experiments. The binding energies (D0) for the successive addition of H2O and Ar to the vanadium cation are 36.2 and 9.4 kcal mol(-1), respectively.
为支持质量选择红外光解离（IRPD）光谱实验，采用了包括所有单双激发（CCSD）以及来自连接三激发的微扰贡献[CCSD(T)]的耦合簇方法来研究V+(H₂O)和ArV+(H₂O)配合物。计算了四个最低能量的五重态（⁵A₁、⁵A₂、⁵B₁和⁵B₂）的平衡几何结构、谐振动频率和解离能，所有这些态都出现在6 kcal mol⁻¹的能量范围内。此外，对V+(H₂O)和ArV+(H₂O)的⁵A₁态进行了具有完整四次力场的非谐振动分析。使用了两种不同的基组：一种是用于O、H和Ar的具有三重ζ加极化（TZP）的Wachters+f V[8s6p4d1f]基组；另一种是用于O和H的具有aug-cc-pVQZ的Ahlrichs QZVPP V[11s6p5d3f2g]和Ar[9s6p4d2f1g]基组。预测V+(H₂O)的基态为⁵A₁，但氩标记使ArV+(H₂O)的最低能量态变为⁵B₁。我们的计算表明，由于H₂O与金属离子的相互作用，其平衡键角打开了2° - 3°。零点振动平均使有效键角进一步增加2.0° - 2.5°，这主要是由于重钒原子的离轴运动，而不是水弯曲势的变化。键角的总理论位移约为 +4°，明显小于从IRPD实验推断出的近9°的拓宽。钒阳离子相继添加H₂O和Ar的结合能（D₀）分别为36.2和9.4 kcal mol⁻¹。
