The lanthanoid hydration properties beyond the ‘Gadolinium Break’: Dysprosium (III) and holmium (III), an ab initio quantum mechanical molecular dynamics study

On the Hydration of the Rare Earth Ions in Aqueous Solution

“…In solution, the local environment varies significantly and slightly different spectrum will result and so the overall spectral shape is significantly broadened. Molecular dynamics (MD) results [45,46] demonstrated the flexibility of the lanthanide hydrate structures such as minor ultrafast geometric modifications within the hydrate or from pseudorotations, requiring substantially longer times in the scale at ca. 1 ps for establishment of an altered geometry [45].…”

“…The vibrational periods of the 1 Ln-OH 2 vibrations range from 0.097 ps for La 3+ to 0.082 ps for Lu 3+ [30,31,35] so that the modes vibrate several hundred thousand times before the hydrated Ln 3+ species experiences a water exchange. (The establishment of slightly altered geometry according to Rode et al [45,46] is of the order of a ps and allows only a few vibrational periods to occur. )…”

“…(More recent data on the rates of water exchange, k 298 ex measured directly by NMR [39,40] correlate closely with the k 298 i values for the RE ions reassuring the validity of the data in [38]). It is worthwhile to mention that recently a plethora of MD results (see for instance [45,46] and references therein) have been published giving structural data for the hydrated rare earth ions and also dynamic parameters. However, the water exchange rates put forward by these theoretical simulations are very short; actually too short to justify the aforementioned experimental values.…”

Topological Study of Bonding in Aquo and Bis(triazinyl)pyridine Complexes of Trivalent Lanthanides and Actinides: Does Covalency Imply Stability?

“…EXAFS data 38 show a reduction in coordination number below nine (though not as low as eight) for Ln > Gd, and a recent ab initio molecular dynamics study of the hydration of Dy(III) and Ho (III) conclude that eight-coordinated complexes are energetically stable 83 . This implies that, for Ln > Gd…”

Theoretical Study of pKa Values for Trivalent Rare-Earth Metal Cations in Aqueous Solution

“…Numerous computation models of metal ion–water complexes suggest that the outer sphere water molecules have a minor impact on the ionic center through hydrogen bonding with coordinated water molecules, but the hydrogen bond is generally extensive among liquid water molecules. ,, Furthermore, rare-earth ions have similar radii and coordination properties; therefore, the differences among the outer spheres of these ions are negligible. Consequently, only water molecules in the first coordination sphere are considered in this work.…”