Magnitude and orientation dependence of intermolecular interaction between perfluoroalkanes: High level ab initio calculations of CF4 and C2F6 dimers

Abstract

Intermolecular interaction energies of eight orientation CF4 dimers and seven orientation C2F6 dimers were calculated with electron correlation correction by the second-order Møller–Plesset perturbation (MP2) method. The D3d CF4 dimer and C2h C2F6 dimer have the largest binding energies. Electron correlation correction increases the attraction considerably, while the effects of electron correlation beyond MP2 are small. Electrostatic and induction energies are not large in all cases. This indicates that dispersion interaction is mainly responsible for the attraction. The calculated binding energy of the CF4 dimer (0.69 kcal/mol) is about 60% larger than that of the CH4 dimer (0.44 kcal/mol), while the binding energy of the C2F6 dimer (1.02 kcal/mol) is close to that of the C2H6 dimer (0.90 kcal/mol). The intermolecular separations (C⋯C distance) in the CF4 and CH4 dimers at the potential minima are close (4.0 and 3.8 Å, respectively), while the separation in the C2F6 dimer (4.8 Å) is appreciably larger than that in the C2H6 dimer (4.0 Å). The larger intermolecular separation in the C2F6 dimer reduces dispersion energy. Therefore the binding energies of the C2F6 and C2H6 dimers are not largely different. The molar volume of C2F6 is substantially larger than that of C2H6 due to bulky fluorine atoms. The small difference of the binding energies suggests that the large molecular volume of perfluoroalkanes is the cause of their small heats of vaporization per volume.

Monolayer Solids of Short Alkanes and Perfluoroalkanes

“…These models also give good overall agreement with the quantum chemistry results 11,12 for dimer energies, as shown in Table 5. The F3 case was already discussed by Tsuzuki et al 12 who concluded that this AA model was a definite improvement on the UA models.…”

Efficient basis sets for non-covalent interactions in XDM-corrected density-functional theory

“…[52][53][54][55][56][57] In this work, we update the reference data for this last set of 17 complexes, to ensure that the full KB49 set of reference data will be of consistently high quality. The updated BEs are collected in Table I, grouped by the dominant interaction type.…”

Trifluoromethyl: An Amphiphilic Noncovalent Bonding Partner

“…[3] CF 3 -groupsa ppear not to repel other negatively polarized groups as strongly as expected and even to enter into "negative-negative" close contacts,m any between CF 3 -groups( self-dimerization). [5] The strongestF ···F interaction reported for the CF 4 dimer is À0.7 kcal mol À1 , [6][7][8] and the energy of as ingle F···F interaction between CF 4 molecules has been estimated to be À0.2 kcal mol À1 . [5] The strongestF ···F interaction reported for the CF 4 dimer is À0.7 kcal mol À1 , [6][7][8] and the energy of as ingle F···F interaction between CF 4 molecules has been estimated to be À0.2 kcal mol À1 .…”

“…[4] NMRr esultss uggest these interactions are strong enough to hinder rotationo ft he CF 3 groups in solution. [8] Since CF 4 does not have ap ermanentd ipole,t he F···F interactions have been suggested to result primarily from dispersion, althoughe lectrostatic interactions may [8] or may not [6] also play as ignificant role. [8] Since CF 4 does not have ap ermanentd ipole,t he F···F interactions have been suggested to result primarily from dispersion, althoughe lectrostatic interactions may [8] or may not [6] also play as ignificant role.…”