Photoemission Spectra and Density Functional Theory Calculations of 3d Transition Metal鈥揂qua Complexes (Ti鈥揅u) in Aqueous Solution

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• 作者：Diana Yepes ; Robert Seidel ; Bernd Winter ; Jochen Blumberger ; Pablo Jaque
• 刊名：Journal of Physical Chemistry B
• 出版年：2014
• 出版时间：June 19, 2014
• 年：2014
• 卷：118
• 期：24
• 页码：6850-6863
• 全文大小：532K
• 年卷期：v.118,no.24(June 19, 2014)
• ISSN：1520-5207

文摘

Photoelectron spectroscopy measurements and density functional calculations are combined to determine the lowest electron binding energies of first-row transition-metal aqua ions, titanium through copper, with 3d¹ through 3d⁹ electronic configurations, in their most common oxidation states. Vertical ionization energies are found to oscillate considerably between 6.76 and 9.65 eV for the dications and between 7.05 and 10.28 eV for the respective trivalent cations. The metal cations are modeled as [M(H₂O)_n]^q+ clusters (q = 2, 3, and 4; n = 6 and 18) surrounded by continuum solvent. The performance of 10 exchange鈥揷orrelation functionals, two GGAs, three MGGAs, two HGGAs and three HMGGAs, combined with the MDF10(ECP)/6-31+G(d,p) basis set is assessed for 11 M鈥揙 bond distances, 10 vertical ionization energies, 6 adiabatic ionization energies, and the associated reorganization free energies. We find that for divalent cations the HGGA and HMGGA functionals in combination with the 18 water model show the best agreement with experimental vertical ionization energies and geometries; for trivalent ions, the MGGA functionals perform best. The corresponding reorganization free energies (位_o) of the oxidized ions are significantly underestimated with all DFT functionals and cluster models. This indicates that the structural reorganization of the solvation shell upon ionization is not adequately accounted for by the simple solvation models used, emphasizing the importance of extended sampling of thermally accessible solvation structures for an accurate computation of this quantity. The photoelectron spectroscopy measurements reported herein provide a comprehensive set of transition-metal redox energetic quantities for future electronic structure benchmarks.