Distorted five-fold coordination of Cu2+(aq) from a Car–Parrinello molecular dynamics simulation

Abstract

The solvation shell structure and dynamics of a single Cu2+ ion in a periodic box with 32 water molecules under ambient conditions has been investigated using Car-Parrinello molecular dynamics simulations in a time-window of 18 ps. Five-fold coordination with four equidistant equatorial water molecules at 2.00 A and one axial water molecule at 2.45 A from the Cu2+ ion is found. A "hole" without water molecules is found on the opposite side of the axial water. The ion-water bonding character for the equatorial water molecules is different from that of the axial water molecules, as shown by a localized orbital analysis of the electronic structure. Moreover, the calculated OD stretching vibrational band for the equatorial water molecules lies ca. 175 cm-1 below the axial-water band, in good agreement with experimental data. The equatorial-water band lies below, and the axial-water band above, the pure liquid D2O band, also in agreement with experimental data.

Calculations of hyperfine coupling constant of copper(II) in aqueous environment. Finite temperature molecular dynamics and relativistic effects

“…On the other hand, Rode and coworkers [19][20][21][22][23] obtained almost exclusively a sixfold coordinated copper(II) with Jahn-Teller distortion of the octahedral ligand field in the presented QM/MM calculations at both Hartree-Fock and B3LYP levels of theory. The only exception found by Rode and coworkers was a resolution of identity BP86 (nonhybrid DFT) calculation [21], which is similar to the BLYP functional calculations employed in the CP simulations [13,18], and which yielded a fivefold to sixfold coordination ratio of ca 60:40 [21]. Concluding that, without the inclusion of exact exchange, the fivefold coordination is becoming more preferred [21].…”

“…According to Pasquarello et al [13], the fivefold coordination was confirmed also by the neutron diffraction methods. Fivefold coordination was also obtained from the (nonhybrid DFT) CP molecular dynamics performed by Amira et al [18]. On the other hand, Rode and coworkers [19][20][21][22][23] obtained almost exclusively a sixfold coordinated copper(II) with Jahn-Teller distortion of the octahedral ligand field in the presented QM/MM calculations at both Hartree-Fock and B3LYP levels of theory.…”

Computational Study of Copper(II) Complexation and Hydrolysis in Aqueous Solutions Using Mixed Cluster/Continuum Models

“…22,23 Surprisingly, the coordination environment even for the simplest hydrated Cu(II) ion has been the subject of extensive debate in recent years. 21,[24][25][26][27][28][29][30][31][32] The most recent X-ray absorption studies (EXAFS and XANES) of aqueous solution of Cu(II), 26 as well as theoretical calculations performed by us 30 and others, 31,32 showed that the [Cu(aq)] 2+ ion can be represented as a five-coordinate square-pyramidal structure with one elongated axial water molecule. Despite the flexibility of the coordination geometry, Cu 2+ is one of the most strongly coordinated divalent transition metal ions.…”

Hydration of Copper(II): New Insights from Density Functional Theory and the COSMO Solvation Model

“…Two independent Car-Parrinello molecular dynamics (MD) simulations performed [using the BLYP functional and a plane-wave basis set] predicted a 5-fold coordination for Cu 2+ . 31,32 In contrast, QM/ MM MD simulations [employing HF, B3LYP, and MP2 levels of theory with the double-valence basis set for water and the comparable LANL2DZ basis set for Cu 2+ ] resulted in predicting exclusively the Jahn-Teller distorted 6-fold coordinated species. [34][35][36][37] A study of the hydration of Cu 2+ by a small number of water molecules may be an important step toward a better understanding of peculiar solvation effects in bulk water.…”