Density Functional Calculations on the Geometries and Dissociation Energies of [M(H2O)6]2+ Ions. M2+ = Cr2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+

Abstract

Full geometry optimizations have been carried out on high-spin hexaaqua complexes of Cr2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+ by the local spin density functional method with non-local corrections using Gaussian-type basis sets. The octahedral molecular arrangement around the Mn2+, Ni2+, and Zn2+ ions optimized were regular, whereas those around the Cr2+, Fe2+, Co2+, and Cu2+ ions were distorted with significant differences in the three kinds of M-O distances. The Jahn-Teller distortion for the Fe2+ and Co2+ complexes was firstly found in the field of computational geometry optimization.

The Jahn‐Teller effect of the Cr2+ ion in aqueous solution: Ab initio QM/MM molecular dynamics simulations

“…Several experimental and theoretical techniques have been performed for evaluating the Jahn‐Teller distortion in the hydrated Cr 2+ ion, with a first peak at 1.99–2.12 Å assigned to “equatorial” Cr 2+ O distances and 2.27–2.50 Å corresponding to “axial” Cr 2+ O distances 2‐6, 8‐12. In the QM/MM simulation, the Jahn‐Teller distortion of the first hydration shell of Cr 2+ is clearly pronounced in the Cr 2+ O RDFs (Fig.…”

“…The hydration of Cr 2+ has been a subject of particular interest for experimental1–9 and theoretical10–12 investigations, due to the Jahn‐Teller distortion expected with a high‐spin 3d 4 electron configuration. The structure of the hydrated Cr 2+ ion was evaluated by the EXAFS method, with Cr 2+ O distances of 1.99 and 2.30 Å for the equatorial and axial Cr 2+ O distances, respectively 2, 3.…”

“…The combination of such HF‐EPR data with a previous electronic absorption spectroscopic investigation1 shows that aqueous Cr 2+ has octahedral‐hexaaquo coordination, with tetragonal elongation, as expected by Jahn‐Teller theory 9. Using the density functional theory, the Cr 2+ O distances were found to be in the range of 2.025–2.268 Å 10. A D 2 h structure of the [Cr(H 2 O) 6 ] 2+ complex, with Cr 2+ O distances in the range of 2.12–2.37 Å, was proposed on the basis of ab initio SCF method 11.…”

Theoretical and experimental investigation of nickel isotopic fractionation in species relevant to modern and ancient oceans

“…Extensive structural studies of Ni(H 2 O) 6 2+ have been carried out (Caminiti et al, 1977;Neilson and Enderby, 1978;Sandstrom, 1979;Magini, 1981;Magini et al, 1982;Waizumi et al, 1992aWaizumi et al, ,b, 1999. In order to evaluate the strength of mass-dependent effects, quantum chemical calculations of the vibrational energies of the hydrated Ni(II) species were performed.…”

Modelling of Octahedral Manganese II Complexes with Inorganic Ligands: A Problem with Spin-States

“…It is usual to assume that octahedral manganese II complexes are high-spin molecules and such an assumption has been widely used in almost every work concerning this type of complexes [1][2]. There are many arguments, both experimental and theoretical, which support this assumption, but some of them can be questioned.…”