Journal article
Density functional theory and thermodynamics analysis of MAl12 Keggin substitution reactions: Insights into ion incorporation and experimental confirmation
The Journal of chemical physics, Vol.154(6), pp.64303-064303
02/14/2021
DOI: 10.1063/5.0038962
PMID: 33588534
Abstract
Polyaluminum cations, such as the MAl12 Keggin, undergo atomic substitutions at the heteroatom site (M), where nanoclusters with M = Al3+, Ga3+, and Ge4+ have been experimentally studied. The identity of the heteroatom M has been shown to influence the structural and electronic properties of the nanocluster and the kinetics of ligand exchange reactions. To date, only three ε-analogs have been identified, and there is a need for a predictive model to guide experiment to the discovery of new MAl12 species. Here, we present a density functional theory (DFT) and thermodynamics approach to predicting favorable heteroatom substitution reactions, alongside structural analyses on hypothetical ε-MAl12 nanocluster models. We delineate trends in energetics and geometry based on heteroatom cation properties, finding that Al3+–O bond lengths are related to heteroatom cation size, charge, and speciation. Our analyses also enable us to identify potentially isolable new ε-MAl12 species, such as FeAl127+. Based upon these results, we evaluated the Al3+/Zn2+/Cr3+ system and determined that substitution of Cr3+ is unfavorable in the heteroatom site but is preferred for Zn2+, in agreement with the experimental structures. Complimentary experimental studies resulted in the isolation of Cr3+-substituted δ-Keggin species where Cr3+ substitution occurs only in the octahedral positions. The isolated structures Na[AlO4Al9.6Cr2.4(OH)24(H2O)12](2,6-NDS)4(H2O)22 (δ-CrnAl13-n-1) and Na[AlO4Al9.5Cr2.5(OH)24(H2O)12](2,7-NDS)4(H2O)18.5 (δ-CrnAl13-n-2) are the first pieces of evidence of mixed Al3+/Cr3+ Keggin-type nanoclusters that prefer substitution at the octahedral sites. The δ-CrnAl13-n-2 structure also exhibits a unique placement of the bound Na+ cation, which may indicate that Cr3+ substitution can alter the surface reactivity of Keggin-type species.
Details
- Title: Subtitle
- Density functional theory and thermodynamics analysis of MAl12 Keggin substitution reactions: Insights into ion incorporation and experimental confirmation
- Creators
- Jennifer L Bjorklund - University of Iowa, Department of Chemistry, Iowa City, Iowa 52245, USAMohammad Shohel - University of Iowa, Department of Chemistry, Iowa City, Iowa 52245, USAJoseph W Bennett - University of Iowa, Department of Chemistry, Iowa City, Iowa 52245, USAJack A Smith - University of Iowa, Department of Chemistry, Iowa City, Iowa 52245, USAMargaret E Carolan - University of Iowa, Department of Chemistry, Iowa City, Iowa 52245, USAEthan Hollar - University of Iowa, Department of Chemistry, Iowa City, Iowa 52245, USATori Z Forbes - University of Iowa, Department of Chemistry, Iowa City, Iowa 52245, USASara E Mason - University of Iowa, Department of Chemistry, Iowa City, Iowa 52245, USA
- Resource Type
- Journal article
- Publication Details
- The Journal of chemical physics, Vol.154(6), pp.64303-064303
- DOI
- 10.1063/5.0038962
- PMID
- 33588534
- ISSN
- 0021-9606
- eISSN
- 1089-7690
- Number of pages
- 13
- Grant note
- 1254127 / Division of Chemistry (https://doi.org/10.13039/100000165)
- Language
- English
- Date published
- 02/14/2021
- Academic Unit
- Civil and Environmental Engineering; Core Research Facilities; Chemistry
- Record Identifier
- 9984216609902771
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