Physical characterization of the state of motion of the phenalenyl spin probe in cation-exchanged faujasite zeolite supercages with pulsed EPR

Effects of tert-Butyl Halide Molecular Siting in Crystalline NaX Faujasite on The Infrared Vibrational Spectra

“…With regard to the study of adsorbate interactions, there is a relatively small range of molecules whose detailed interactions with NaX have been reported. Representative examples of molecular interactions with NaX and the various techniques to study them include hydrochlorofluorocarbons via nuclear magnetic resonance, X-ray and neutron diffraction and modeling studies, aromatic hydrocarbon and nitroxide free radical spin probes via electron paramagnetic resonance, methylamine by infrared spectrometry, furan by combined infrared and inelastic neutron scattering spectrometries, and water by X-ray diffraction . These studies have revealed often-subtle effects of guest adsorption in NaX, typically on such phenomena as coordination with Na and cation binding dynamics.…”

A Magnetic Resonance Study of Complex Formation between the Neutral Phenalenyl Radical and Alkali Metal Ions in Dilute Alcohol Solutions

“…Understanding the nature of such a complex may be important in revealing the unique catalytic properties of these zeolites. Phenalenyl (I) undergoes predominantly in-plane reorientation in the NaX zeolite cage to about 200 K. , Above this temperature, the molecule approaches a free, isotropic rotation, as out-of-plane reorientations catch up with rapid, in-plane reorientation. , Studies of the relatively small activation energies on exchanged cation are consistent with a model 1 in which there is a bonding interaction between the π-system of the phenalenyl ring system and the empty s-orbital of the cation. The bond remains substantially intact, while the phenalenyl reorients in its plane but is broken when it reorients out-of-plane.…”

“…In previous work we have studied the molecular motion of phenalenyl (PNL) (I) in the supercage of cation exchanged X- and Y-zeolites using CW- and pulsed-EPR techniques. This study indicated a possible correlation between the CW EPR spectrum of the neutral phenalenyl radical and the nuclear magnetic moments of the exchanged alkali metal cations Li + , Na + , K + , Rb + , and Cs + . This correlation is believed to result from the formation of a PNL-cation Lewis acid−base complex.…”

“…An isotropic 23 Na hyperfine term was added to the previous Hamiltonian for PNL 17 and a Lorentzian rather than Gaussian line width function was employed. The simulated spectra were least-squares fit to the experimental spectra for the PNL−Na + solutions with [Na + ] 0 = 1.0 M and [Na + ] 0 = 0.01 M using a previously described procedure . The isotropic g values determined above for both samples were kept constant while the isotropic 1 H hyperfine frequencies for the meta, a m , and para, a p , protons in PNL, the isotropic 23 Na hyperfine frequency, a Na , and the Lorentzian line width, Δ H , were allowed to least-squares fit to the spectra.…”