Solid-state 27Al NMR spectroscopy of the γ-Al13 Keggin containing Al coordinated by a terminal hydroxyl ligand

Brian L. Phillips, Andy Ohlin, John Vaughn, William Woerner, Scott Smart, Ravi Subramanyam, Long Pan

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Abstract

We report solid-state27Al NMR spectroscopic results for the sulfate salt of the γ-Al13 Keggin cluster, γ-[AlO4Al12(OH)25(OH2)11][SO4]3·[H2O]14, that provide a spectroscopic signature for partial hydrolysis of this Keggin-type cluster. In 27Al multiple-quantum magic-angle spinning NMR spectra, all 13 Al positions of the cluster are at least partially resolved and assigned with the aid of density functional theory (DFT) calculations of the 27Al electric field gradients. The isotropic chemical shift of the single tetrahedral site, 75.7 ppm, is nearly identical to that reported for solutions from which the cluster crystallizes. Reflecting broadly similar coordination environments, the octahedral Al show mostly small variations in isotropic chemical shift (+7 to +11 ppm) and quadrupolar coupling constant (CQ; 6-7.5 MHz), except for one resonance that exhibits a much smaller CQ and another site with a larger value. DFT calculations show that deprotonation of a terminal water ligand, to form an η-OH group, causes a large reduction in the 27Al CQ, allowing assignment of a distinct, narrow peak for octahedral Al to this hydroxyl-terminated site. This result suggests a relationship between octahedral 27Al NMR line width and hydrolysis for solids prepared from Keggin-type clusters.

Original languageEnglish
Pages (from-to)12270-12280
Number of pages11
JournalInorganic Chemistry
Volume55
Issue number23
DOIs
Publication statusPublished - 5 Dec 2016

Cite this

Phillips, B. L., Ohlin, A., Vaughn, J., Woerner, W., Smart, S., Subramanyam, R., & Pan, L. (2016). Solid-state 27Al NMR spectroscopy of the γ-Al13 Keggin containing Al coordinated by a terminal hydroxyl ligand. Inorganic Chemistry, 55(23), 12270-12280. https://doi.org/10.1021/acs.inorgchem.6b01968
Phillips, Brian L. ; Ohlin, Andy ; Vaughn, John ; Woerner, William ; Smart, Scott ; Subramanyam, Ravi ; Pan, Long. / Solid-state 27Al NMR spectroscopy of the γ-Al13 Keggin containing Al coordinated by a terminal hydroxyl ligand. In: Inorganic Chemistry. 2016 ; Vol. 55, No. 23. pp. 12270-12280.
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abstract = "We report solid-state27Al NMR spectroscopic results for the sulfate salt of the γ-Al13 Keggin cluster, γ-[AlO4Al12(OH)25(OH2)11][SO4]3·[H2O]14, that provide a spectroscopic signature for partial hydrolysis of this Keggin-type cluster. In 27Al multiple-quantum magic-angle spinning NMR spectra, all 13 Al positions of the cluster are at least partially resolved and assigned with the aid of density functional theory (DFT) calculations of the 27Al electric field gradients. The isotropic chemical shift of the single tetrahedral site, 75.7 ppm, is nearly identical to that reported for solutions from which the cluster crystallizes. Reflecting broadly similar coordination environments, the octahedral Al show mostly small variations in isotropic chemical shift (+7 to +11 ppm) and quadrupolar coupling constant (CQ; 6-7.5 MHz), except for one resonance that exhibits a much smaller CQ and another site with a larger value. DFT calculations show that deprotonation of a terminal water ligand, to form an η-OH group, causes a large reduction in the 27Al CQ, allowing assignment of a distinct, narrow peak for octahedral Al to this hydroxyl-terminated site. This result suggests a relationship between octahedral 27Al NMR line width and hydrolysis for solids prepared from Keggin-type clusters.",
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Phillips, BL, Ohlin, A, Vaughn, J, Woerner, W, Smart, S, Subramanyam, R & Pan, L 2016, 'Solid-state 27Al NMR spectroscopy of the γ-Al13 Keggin containing Al coordinated by a terminal hydroxyl ligand', Inorganic Chemistry, vol. 55, no. 23, pp. 12270-12280. https://doi.org/10.1021/acs.inorgchem.6b01968

Solid-state 27Al NMR spectroscopy of the γ-Al13 Keggin containing Al coordinated by a terminal hydroxyl ligand. / Phillips, Brian L.; Ohlin, Andy; Vaughn, John; Woerner, William; Smart, Scott; Subramanyam, Ravi; Pan, Long.

In: Inorganic Chemistry, Vol. 55, No. 23, 05.12.2016, p. 12270-12280.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Solid-state 27Al NMR spectroscopy of the γ-Al13 Keggin containing Al coordinated by a terminal hydroxyl ligand

AU - Phillips, Brian L.

AU - Ohlin, Andy

AU - Vaughn, John

AU - Woerner, William

AU - Smart, Scott

AU - Subramanyam, Ravi

AU - Pan, Long

PY - 2016/12/5

Y1 - 2016/12/5

N2 - We report solid-state27Al NMR spectroscopic results for the sulfate salt of the γ-Al13 Keggin cluster, γ-[AlO4Al12(OH)25(OH2)11][SO4]3·[H2O]14, that provide a spectroscopic signature for partial hydrolysis of this Keggin-type cluster. In 27Al multiple-quantum magic-angle spinning NMR spectra, all 13 Al positions of the cluster are at least partially resolved and assigned with the aid of density functional theory (DFT) calculations of the 27Al electric field gradients. The isotropic chemical shift of the single tetrahedral site, 75.7 ppm, is nearly identical to that reported for solutions from which the cluster crystallizes. Reflecting broadly similar coordination environments, the octahedral Al show mostly small variations in isotropic chemical shift (+7 to +11 ppm) and quadrupolar coupling constant (CQ; 6-7.5 MHz), except for one resonance that exhibits a much smaller CQ and another site with a larger value. DFT calculations show that deprotonation of a terminal water ligand, to form an η-OH group, causes a large reduction in the 27Al CQ, allowing assignment of a distinct, narrow peak for octahedral Al to this hydroxyl-terminated site. This result suggests a relationship between octahedral 27Al NMR line width and hydrolysis for solids prepared from Keggin-type clusters.

AB - We report solid-state27Al NMR spectroscopic results for the sulfate salt of the γ-Al13 Keggin cluster, γ-[AlO4Al12(OH)25(OH2)11][SO4]3·[H2O]14, that provide a spectroscopic signature for partial hydrolysis of this Keggin-type cluster. In 27Al multiple-quantum magic-angle spinning NMR spectra, all 13 Al positions of the cluster are at least partially resolved and assigned with the aid of density functional theory (DFT) calculations of the 27Al electric field gradients. The isotropic chemical shift of the single tetrahedral site, 75.7 ppm, is nearly identical to that reported for solutions from which the cluster crystallizes. Reflecting broadly similar coordination environments, the octahedral Al show mostly small variations in isotropic chemical shift (+7 to +11 ppm) and quadrupolar coupling constant (CQ; 6-7.5 MHz), except for one resonance that exhibits a much smaller CQ and another site with a larger value. DFT calculations show that deprotonation of a terminal water ligand, to form an η-OH group, causes a large reduction in the 27Al CQ, allowing assignment of a distinct, narrow peak for octahedral Al to this hydroxyl-terminated site. This result suggests a relationship between octahedral 27Al NMR line width and hydrolysis for solids prepared from Keggin-type clusters.

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