PCCP Blog

Researchers in the group of Professor Martina Havenith at the Ruhr-University Bochum have shown that terahertz spectroscopy can be used, employing meticulous physical chemical considerations, to open a window into the solvation of ions in solution. In this paper they join the discussion regarding the solvation of trivalent lanthanide ions in water, by studying lanthanum chloride and bromide at different concentrations. They determine association constants for the ion pairs and investigate the nature of the lanthanide solvation—adding the experimental support to the proponents of outer-sphere interaction between anions and trivalent lanthanide ions in solution.

Sharma and co-workers investigate the ion pairing of lanthanum halides from a true physical chemical approach. A puritan approach that to me, make this paper a pivotal example of what a PCCP paper should be. Is should not necessarily following the most recent trend, but answer or address an important question. Here, the hydration of lanthanide ions. We do not know the structure of solvation lanthanide ions, even the stoichiometry is unknown. Except for an assumption that lanthanum has nine water molecules in the ligand sphere forming a symmetrical tricapped trigonal prism, the paper attacks the question of lanthanide solvation from a refreshingly new angle.

The image attached to this post shows how well terahertz spectroscopy can describe a solution of ions. Remembering that this image is generated from several layers of a priori information, such as the behavior of neat water, simple electrolytes, solutions of alkali halides etc. I strongly recommend that you read the paper is you are interested in the rare earths, electrolytes or specific ion effects.

by Dr Thomas Just Sørensen

Read this exciting PCCP article today:

From solvated ions to ion-pairing: a THz study of lanthanum(III) hydration
Vinay Sharma, Fabian Böhm, Michael Seitz, Gerhard Schwaab and Martina Havenith
Phys. Chem. Chem. Phys. 2013, 15, 8383-8391
DOI: 10.1039/C3CP50865J

It’s no secret that I find rare gas chemistry very exciting, so when I came across this article by Jien-Lian Chen et al. I knew immediately that it would form the subject of my next blog post. The group, based in Taiwan, have performed calculations that predict a new series of rare gas molecules. Whilst this is, in itself, an exciting achievement, what really grabbed me was that they predict these molecules to be relatively stable – stable enough to be detected experimentally.

As far as I am aware, that is the holy grail of theoretical rare gas chemistry, as there is still very little experimental data on molecules of this kind. The group’s calculations were rigorous, comparing a variety of high-level computational methods and finding good agreement between them. They predicted the strength of the bonds to be significant, and examined the most likely unimolecular dissociation pathways and found sizable barriers to each of them for this class of molecule. All this adds up to a real possibility for generating some new, experimental rare gas data.

So what are these fantastic new molecules? They take the general form F–RG–BNR, where RG can be Argon, Krypton or Xenon, and R can be quite a variety of small groups. Interestingly, they found that the stability of the molecule was largely unaffected by the identity of the R group, indicating that it may be possible to study even more of them than were covered in this investigation.

All we need now is for somebody to work out how to synthesise these molecules in a spectroscopically useful environment, and perform the experiments to confirm the theoretical predictions. Experimental spectroscopists, consider the challenge issued!

By Victoria Wilton

Read the full details of this PCCP article:

Theoretical prediction of new noble-gas molecules FNgBNR (Ng = Ar, Kr, and Xe; R = H, CH₃, CCH, CHCH₂, F, and OH)
Jien-Lian Chen, Chang-Yu Yang, Hsiao-Jing Lin and Wei-Ping Hu
Phys. Chem. Chem. Phys., 2013, 15, 9701-9709
DOI: 10.1039/C3CP50447F