Encapsulation of Xenon by a Self-Assembled Fe₄L₆ Metallosupramolecular Cage

We report ¹²⁹Xe 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 ¹²⁹Xe 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

Experimental and First-Principles NMR Analysis of Pt(II) Complexes With <i>O</i>,<i>O</i>′‑Dialkyldithiophosphate Ligands

Polycrystalline bis­(dialkyldithiophosphato)­Pt­(II) complexes of the form [Pt­{S₂P­(OR)₂}₂] (R = ethyl, <i>iso</i>-propyl, <i>iso</i>-butyl, <i>sec</i>-butyl or <i>cyclo</i>-hexyl group) were studied using solid-state ³¹P and ¹⁹⁵Pt NMR spectroscopy, to determine the influence of R to the structure of the central chromophore. The measured anisotropic chemical shift (CS) parameters for ³¹P and ¹⁹⁵Pt afford more detailed chemical and structural information, as compared to isotropic CS and <i>J</i> couplings alone. Advanced theoretical modeling at the hybrid DFT level, including both crystal lattice and the important relativistic spin–orbit effects qualitatively reproduced the measured CS tensors, supported the experimental analysis, and provided extensive orientational information. A particular correction model for the non-negligible lattice effects was adopted, allowing one to avoid a severe deterioration of the ¹⁹⁵Pt anisotropic parameters due to the high requirements posed on the pseudopotential quality in such calculations. Though negligible differences were found between the ¹⁹⁵Pt CS tensors with different substituents R, the ³¹P CS parameters differed significantly between the complexes, implying the potential to distinguish between them. The presented approach enables good resolution and a detailed analysis of heavy-element compounds by solid-state NMR, thus widening the understanding of such systems