Cuⁱⁱ in Liquid Ammonia: An Approach by Hybrid Quantum‐Mechanical/Molecular‐Mechanical Molecular Dynamics Simulation

Abstract

To investigate the solvation structure of the Cu(II) ion in liquid ammonia, ab initio quantum-mechanical/molecular-mechanical (QM/MM) molecular dynamics (MD) simulations were carried out at Hartree Fock (HF) and hybrid density functional theory (B3 LYP) levels. A sixfold-coordinated species was found to be predominant in the HF case whereas five- and sixfold-coordinated complexes were obtained in a ratio 2:1 from the B3 LYP simulation. In contrast to hydrated Cu(II), which exhibits a typical Jahn-Teller distortion, the geometrical arrangement of ligand molecules in the case of ammonia can be described as a [2 + 4] ([2 + 3]) configuration with 4 (3) elongated copper-nitrogen bonds. First shell solvent exchange reactions at picosecond rate took place in both HF and B3 LYP simulations, again in contrast to the more stable sixfold-coordinated hydrate. NH3 ligands apparently lead to strongly accelerated dynamics of the Cu(II) solvate due to the "inverse" [2 + 4] structure with its larger number of elongated copper-ligand bonds. Several dynamical properties, such as mean ligand residence times or ion-ligand stretching frequencies, prove the high lability of the solvated complex.

Combined Ab Initio Computational and Infrared Spectroscopic Study of the cis- and trans-Bis(glycinato)copper(II) Complexes in Aqueous Environment

“…The main advantage of this extension is the possible renunciation of non-Coulombic interaction potentials between core zone particles and particles located in the MM region. The versatility of this framework has been proven in the past for cations, − anions, , as well as small organic molecules. , The simulations of the two isomers were carried out in cubic boxes with a side length of 39.2 Å, each containing 2000 water molecules. As Cu(II) was placed in the center of the core region, its radius was chosen to be 1.0 Å.…”

Microscopic Insights into Extraction Mechanism of Copper(II) in Ammoniacal Solutions Studied by X-ray Absorption Spectroscopy and Density Functional Theory Calculation

“…The mean bonding energy evidently increases from the 59.9 kcal/mol for [Cu­(H 2 O) 6 ] 2+ to the 92.6 kcal/mol for [Cu­(NH 3 ) 4 ] 2+ . Thus, the stability increase of copper­(II) species in ammoniacal solutions could result in the decrease of their reactivity. , …”

A Comparative Study of [CaEDTA]2– and [MgEDTA]2–: Structural and Dynamical Insights from Quantum Mechanical Charge Field Molecular Dynamics

“…It has been previously shown that the water exchange at several metal ions including calcium(II) significantly increases upon complexation by heteroatoms such as nitrogen. [75][76][77][78] Also in our case EDTA is coordinating with two nitrogen atoms towards the calcium(II) ion and the mean residence time for water drops approx. an order magnitude from 40-60 ps to 2.75 ps, thus being in accordance with the literature.…”