Guest-Host Interactions in Sodium Zeolite Y: Structural and Dynamical ²³Na Double-Rotation NMR Study of H₂O, PMe₃, Mo(CO)₆, and Mo(CO)₄(PMe₃)₂ Adsorption in Na₅₆Y

²³Na double-rotation NMR (DOR) provides site-specific structural and dynamical information on guest-host interactions within sodium zeolite Y pores. Quantitative adsorption of H₂O, PMe₃, and Mo(CO)₆ guests affects both the positions and line shapes of the ²³Na resonances from specific extraframework Na⁺ sites. The evolution of the ²³Na DOR spectra with the progressive introduction of guest molecules allows one to probe direct “solvation” effects involving the Na⁺ cations in the larger supercages, as well as indirect effects on the Na⁺ cations in adjacent smaller sodalite cavities. ²³Na DOR experiments conducted at two magnetic field strengths confirm that PMe₃ coadsorption in 8{Mo(CO)₆},16{PMe₃}-Na₅₆Y, and PMe₃ ligand-substitution in 8{cis-Mo(CO)₄(PMe₃)₂]-Na₅₆Y give rise to progressive deshielding and enhanced quadrupolar interactions of the anchoring Na⁺ cations in the α-cages, relative to those of the starting material, 8{Mo(CO)₆}−Na₅₆Y. Spin-lattice relaxation measurements indicate that adsorption of PMe₃ facilitates an increased motion of the Na⁺ cations and/or guest species inside the α-cages.