Orientation and binding of cyclohexadienyl radical in NaY zeolite—computational study and comparison with benzene

• Published in: Physica. B, Condensed matter Vol. 326; no. 1; pp. 68 - 71
• Main Authors: Macrae, R.M., Webster, B.C.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.02.2003; Elsevier
• Subjects: Chemistry; Density functional theory; Exact sciences and technology; General and physical chemistry; Hartree–Fock Theory; Ion-exchange; Radicals; Surface physical chemistry; Zeolites; 33.15.Pw; 82.75.Mj; Hartree–Fock Theory; 82.75.Jn; 31.50.Bc; Density functional theory; 31.15.Ew; Zeolites; Radicals; Ab initio method; Hartree Fock theory; Zeolite; Molecular sieve; 82.75.Mj: 82.75.Jn; Hartree-Fock Theory; 31.15.Ew Radicals; Density functional; Adsorption; Organic free radical; Benzene; Adsorbed state; Comparative study
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/S0921-4526(02)01578-8

Recent experimental studies suggest that the host–guest interaction is stronger between C 6H 6Mu and the cation site in NaY zeolite than in the case for benzene, leading to trapping of the radical in an essentially frozen geometry over the temperature range 3–322 K. while benzene exhibits fast rotational motion at these temperatures (J. Phys. Chem. B 106 (2002) 6395). A comparison of the benzene–Na + and cyclohexadienyl–Na + model systems using ab initio methods shows that the binding energies between these systems are virtually identical. However, modeling of the benzene and cyclohexadienyl interactions with a partially optimized segment of the zeolite matrix corresponding to the Na + site indicates that electrostatic dipole–dipole interactions between the radical and the zeolite lead to orienting forces (and a barrier to uniaxial reorientation of several tens of kJ mol −1) which do not exist in the case of benzene.