Inelastic neutron scattering spectroscopy of C₆₀@calix[8]arene

Abstract

The vibrational dynamics of the p-tert-butylcalix[8]arene and the 1: 1 inclusion complex C60@p-tert-butylcalix[8]arene are investigated by a combination of inelastic neutron scattering (INS) and MM3 molecular mechanics calculations. The results show that the isolated, single molecule approximation breaks down and is not sufficient to explain the features observed experimentally. The origin of the line broadening in the low energy region is discussed in terms of intermolecular interactions: this effect is sharper in the case of the complex with the C60 molecule, due to the high number of co-conformers allowed by the mismatch between the circumferences of the host and the guest. The successful interpretation of the INS spectra validates the use of the model adopted.

A model equation of state of liquid C60and thermodynamic properties along the liquid–vapour coexistence curve

“…The structure of liquid C 60 is still of considerable interest [5]. Recently, inelastic neutron scattering spectroscopy experiments [6] have provided useful information on the complicated C 60 structure and on the intermolecular interactions.…”

“…According to Girifalco, the best values of A, B and d were obtained by fitting the experimental data for the heat of sublimation and the lattice constant of the FCC crystal. This procedure gives d = 7.1 Å, A = 32.0 × 10 −60 erg cm 6 and B = 55.77 × 10 −105 erg cm 12 . Cheng et al [13] and Cheng and Klein [23] used A = 23.8 × 10 −60 erg cm 6 and B = 36.88 × 10 −105 erg cm 12 .…”

Molecular recognition of p - tert -butylcalixarenes by surface-linked fullerenes C 60 and C 70

“…1, where the 4-, 6-and 8-membered p-tert-butylcalixarenes are simultaneously screened for their binding preferences. While the smallest calix [4]arene shows a small (but nevertheless measurable) binding af®nity for the two immobilized fullerenes, its complexation ability is not comparable with those of the larger macrocycles, at least under our experimental conditions. In the following discussion we will focus only on the relative retentions of the 6-and 8-membered calixarenes.…”

“…Thermodynamic parameters for the association of p-tert-butylcalix[n]arenes with silica bound fullerenes Si±C 60 and Si±C 70 Si±C 60 Si±C 70 Compound DH a (kJ/mol) DS b (J/mol K) DH a (kJ/mol) DS b (J/mol K)The complexation of C 60 by calix[4]naphthalenes in toluene solutions, on the other hand, is accompanied by DH changes between 259.8 and 277.4 kJ/mol and by DS changes between 20.14 and 20.20 kJ/mol K, corresponding to K ass in the 6±7£10 2 M 21 range at 258C. The larger aromatic surfaces of calix[4]naphthalenes, compared to those of simple calixarenes, are thus better suited to establish attractive interactions with the convex surface of C 60 .…”

Probing Vibrational Dynamics of Hydrogen-Bonded Inclusion Compounds with Inelastic Neutron Scattering and Ab Initio Calculations

“…Due to the computational costs associated with DFT methods performed on systems with large numbers of atoms, however, this method has been somewhat limited in its application to inclusion compounds. Experimental INS studies of inclusion compounds based on urea − and calixarene hosts , have been performed and compared with spectra calculated using molecular dynamics and molecular mechanics calculations, respectively. Theoretical ab initio calculations have been used to calculate the vibrational spectrum of large catenane , molecular systems.…”