Theoretical study of the geometrical and electronic structures and thermochemistry of spherophanes

ISSN： 1610-2940

Source： Journal of Molecular Modeling, Vol.15, Iss.9, 2009-09, pp. : 1067-1078

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Abstract

A set of supramolecular cage-structures—spherophanes—was studied at the density functional B3LYP level. Full geometrical structure optimisations were made with 6-31G and 6-31G(d) basis sets followed by frequency calculations, and electronic energies were evaluated at B3LYP/6-31++G(d,p). Three different symmetries were considered: C1, Ci, and Oh. It was found that the bonds between the benzene rings are very long to allow π-electron delocalisation between them. These spherophanes show portal openings of 2.596 Å in Spher1, 4.000 Å in Meth2, 3.659 Å in Oxa3, and 4.412 Å in Thia4. From the point of view of potential host-guest interaction studies, it should also be noted that the atoms nearest to the centre of the cavities are carbons bonded to X groups. These supramolecules seem to exhibit relatively large gap HOMO−LUMO: 2.89 eV(Spher1), 5.26 eV(Meth2), 5.73 eV(Oxa3), and 4.82 eV(Thia4). The calculated ΔH°_f (298.15 K) values at B3LYP/6-31G(d) are (in kcal mol⁻¹) 750.98, 229.78, −10.97, and 482.49 for Spher1, Meth2, Oxa3, and Thia4, respectively. Using homodesmotic reactions, relative to Spher1, the spherophanes Meth2, Oxa3, and Thia4 are less strained by −399.13 kcal mol⁻¹, −390.40 kcal mol⁻¹, and −411.38 kcal mol⁻¹, respectively. Their infrared and ¹³C NMR calculated spectra are reported.