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

✍ Scribed by Christian F. Schwenk; Bernd M. Rode

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 170 KB
• Volume: 5
• Category: Article
• ISSN: 1439-4235
• DOI: 10.1002/cphc.200300972

✦ Synopsis

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. NH~3~ 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.