Encapsulation of Xenon by a Self-Assembled Fe₄L₆ Metallosupramolecular Cage

Abstract

We report (129)Xe NMR experiments showing that a Fe4L6 metallosupramolecular cage can encapsulate xenon in water with a binding constant of 16 M(-1). The observations pave the way for exploiting metallosupramolecular cages as economical means to extract rare gases as well as (129)Xe NMR-based bio-, pH, and temperature sensors. Xe in the Fe4L6 cage has an unusual chemical shift downfield from free Xe in water. The exchange rate between the encapsulated and free Xe was determined to be about 10 Hz, potentially allowing signal amplification via chemical exchange saturation transfer. Computational treatment showed that dynamical effects of Xe motion as well as relativistic effects have significant contributions to the chemical shift of Xe in the cage and enabled the replication of the observed linear temperature dependence of the shift.

Mechanisms and Beyond: Elucidation of Fluxional Dynamics by Exchange NMR Spectroscopy

“…Spacious [Fe 4 L 6 ] 4− metallosupramolecular cage 85 was studied by Lantto, Telkki and co‐workers . Hyperpolarised 129 Xe‐ 29 Xe EXSY was used to calculate an exchange rate of k ex =10 s −1 between free and encapsulated xenon.…”

Electron and nuclear spin polarization in Rb-Xe spin-exchange optical hyperpolarization

“…The exponents of f functions are listed in Table S2 of the Supplemental Material of Ref. [51]. We tested the larger basis set at three Rb-Xe internuclear distances, 3, 5.4, and 7Å, to provide an estimate of the basis-set error, by which we corrected the CCSD(T) results obtained with the 428-function basis.…”

Reversible Encapsulation of Xenon and CH2Cl2 in a Solid‐State Molecular Organometallic Framework (Guest@SMOM)

“…[15] Interestingly the 31 P{ 1 H} SSNMR spectrum now shows sharp signals at d À23. [21] It also shows binding affinity in supramolecular cages, [22] oxide frameworks, [23] MOFs, [24] cryptophanes, [25] and porous coordinationcomplex salts; [26] and has been widely used as an NMR probe for the determination of pore size in framework materials, [27] due to the sensitivity of d( 129 Xe) to its local environment. This transformation is reversible,a nd when [20] V Xe /V cavity = 0.43).…”