Making Amines Strong Bases: Thermodynamic Stabilization ofProtonated Guests in a Highly-Charged Supramolecular Host

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A highly-charged, cavity-containing supramolecular assembly formed by metal-ligand interactions acts as a host to dramatically shift the effective basicity of encapsulated protonated amine guests. The scope of encapsulated protonated amine and phosphine guests shows size selectivity consistent with a constrained binding environment. Protonation of the encapsulated guests is confirmed by {sup 31}P NMR studies, mass spectrometry studies, and the pH dependence of guest encapsulation. Rates of guest self-exchange were measured using the Selective Inversion Recovery method and were found to correlate with the size rather than the basicity of the guests. The activation parameters for guest self-exchange are consistent with ... continued below

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Pluth, Michael D.; Bergman, Robert G. & Raymond, Kenneth N. April 16, 2007.

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A highly-charged, cavity-containing supramolecular assembly formed by metal-ligand interactions acts as a host to dramatically shift the effective basicity of encapsulated protonated amine guests. The scope of encapsulated protonated amine and phosphine guests shows size selectivity consistent with a constrained binding environment. Protonation of the encapsulated guests is confirmed by {sup 31}P NMR studies, mass spectrometry studies, and the pH dependence of guest encapsulation. Rates of guest self-exchange were measured using the Selective Inversion Recovery method and were found to correlate with the size rather than the basicity of the guests. The activation parameters for guest self-exchange are consistent with the established mechanism for guest exchange. The binding constants of the protonated amines are then used to calculate the effective basicity of the encapsulated amines. Depending on the nature of the guest, shifts in the effective basicities of the encapsulated amines of up to 4.5 pK{sub a} units are observed, signifying a substantial stabilization of the protonated form of the guest molecule and effectively making phosphines and amines strong bases.

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  • Journal Name: Journal of the American Chemical Society; Journal Volume: 129; Related Information: Journal Publication Date: 09/19/2007

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  • Report No.: LBNL--63653
  • Grant Number: DE-AC02-05CH11231
  • Grant Number: NSF:2004016723
  • DOI: 10.1021/ja072654e | External Link
  • Office of Scientific & Technical Information Report Number: 928890
  • Archival Resource Key: ark:/67531/metadc896519

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  • April 16, 2007

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  • Sept. 27, 2016, 1:39 a.m.

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  • Dec. 15, 2016, 1:26 p.m.

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Pluth, Michael D.; Bergman, Robert G. & Raymond, Kenneth N. Making Amines Strong Bases: Thermodynamic Stabilization ofProtonated Guests in a Highly-Charged Supramolecular Host, article, April 16, 2007; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc896519/: accessed May 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.