Universität zu Köln

Zhang, Jun, Heinz, Norah and Dolg, Michael ORCID: 0000-0002-0538-0837 (2014). Understanding Lanthanoid(III) Hydration Structure and Kinetics by Insights from Energies and Wave functions. Inorg. Chem., 53 (14). S. 7700 - 7709. WASHINGTON: AMER CHEMICAL SOC. ISSN 1520-510X

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Abstract

The hydration of all trivalent lanthanoid (Ln) ions is studied theoretically from two aspects: energy and wave function. With the help of the incremental scheme, for the first time the lanthanoid(III) aqua complexes are computed at the CCSD(T) level using large basis sets. These computations prove that SCS-MP2 is nearly as accurate as CCSD, thus enabling us to give the most accurate first principle hydration Gibbs free energies and reliable preferred coordination numbers (CNs) of lanthanoid(III) aqua complexes: 9, 8, and both, for light, heavy, and intermediate lanthanoids, respectively. Then a series of wave function analyses were performed to explore the deeper reasons for the preference of specific CNs. An unexpected observation is that as Ln goes from samarium to lutetium, the capping Ln-O bonds in nona-aqua lanthanoid complexes become weaker while they get shorter. Therefore, as the capping Ln-O bonds are getting easier to disrupt, heavier lanthanoids will prefer a low CN, i.e., 8. On the basis of this and previous work of other groups, a model for the water exchange kinetics of lanthanoid(III) ions is proposed. This model suggests that the capping Ln-O bonds of moderate strength, which occur for intermediate lanthanoids, are advantageous for the formation of a bicapped trigonal prism intermediate during water exchange. This explains some NMR experiments and, more importantly, an observation which puzzled investigators for a long time, i.e., that the exchange rate reaches a maximum for the middle region but is low at the beginning and end of the lanthanoid series. This nontrivial behavior of capping Ln-O bonds is interpreted and is believed to determine the hydration behavior of lanthanoid(III) ions.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Zhang, Jun UNSPECIFIED UNSPECIFIED UNSPECIFIED Heinz, Norah UNSPECIFIED UNSPECIFIED UNSPECIFIED Dolg, Michael UNSPECIFIED orcid.org/0000-0002-0538-0837 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-433796
DOI:	10.1021/ic500991x
Journal or Publication Title:	Inorg. Chem.
Volume:	53
Number:	14
Page Range:	S. 7700 - 7709
Date:	2014
Publisher:	AMER CHEMICAL SOC
Place of Publication:	WASHINGTON
ISSN:	1520-510X
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Theoretical Chemistry
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language VALENCE BASIS-SETS; AB-INITIO; ELECTRON-DENSITY; CONTRAST AGENTS; LANTHANIDE; WATER; IONS; COMPLEXES; HYDROGEN; MODEL Multiple languages Chemistry, Inorganic & Nuclear Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/43379