Making Amines Strong Bases: Thermodynamic Stabilization ofProtonated Guests in a Highly-Charged Supramolecular Host
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.
- Research Organization:
- Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
- Sponsoring Organization:
- USDOE Director, Office of Science; National ScienceFoundation
- DOE Contract Number:
- AC02-05CH11231
- OSTI ID:
- 928890
- Report Number(s):
- LBNL--63653; BnR: KC0302010
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Vol. 129; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
Similar Records
Proton Mediated Chemistry and Catalysis in a Self-Assembled Supramolecular Host
Acid Catalysis in Basic Solution: A Supramolecular Host PromotesOrthoformate Hydrolysis