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Issue 6, 2007
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Stabilisation energy of C6H6⋯C6X6 (X = F, Cl, Br, I, CN) complexes: complete basis set limit calculations at MP2 and CCSD(T) levels

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Abstract

Stabilisation energies of stacked structures of C6H6⋯C6X6 (X = F, Cl, Br, CN) complexes were determined at the CCSD(T) complete basis set (CBS) limit level. These energies were constructed from MP2/CBS stabilisation energies and a CCSD(T) correction term determined with a medium basis set (6-31G**). The former energies were extrapolated using the two-point formula of Helgaker et al. from aug-cc-pVDZ and aug-cc-pVTZ Hartree–Fock energies and MP2 correlation energies. The CCSD(T) correction term is systematically repulsive. The final CCSD(T)/CBS stabilisation energies are large, considerably larger than previously calculated and increase in the series as follows: hexafluorobenzene (6.3 kcal mol−1), hexachlorobenzene (8.8 kcal mol−1), hexabromobenzene (8.1 kcal mol−1) and hexacyanobenzene (11.0 kcal mol−1). MP2/SDD** relativistic calculations performed for all complexes mentioned and also for benzenehexaiodobenzene have clearly shown that due to relativistic effects the stabilisation energy of the hexaiodobenzene complex is lower than that of hexabromobenzene complex. The decomposition of the total interaction energy to physically defined energy components was made by using the symmetry adapted perturbation treatment (SAPT). The main stabilisation contribution for all complexes investigated is due to London dispersion energy, with the induction term being smaller. Electrostatic and induction terms which are attractive are compensated by their exchange counterparts. The stacked motif in the complexes studied is very stable and might thus be valuable as a supramolecular synthon.

Graphical abstract: Stabilisation energy of C6H6⋯C6X6 (X = F, Cl, Br, I, CN) complexes: complete basis set limit calculations at MP2 and CCSD(T) levels

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Publication details

The article was received on 20 Oct 2006, accepted on 30 Nov 2006 and first published on 19 Dec 2006


Article type: Paper
DOI: 10.1039/B615318F
Citation: Phys. Chem. Chem. Phys., 2007,9, 755-760
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    Stabilisation energy of C6H6⋯C6X6 (X = F, Cl, Br, I, CN) complexes: complete basis set limit calculations at MP2 and CCSD(T) levels

    K. Pluháčková, P. Jurečka and P. Hobza, Phys. Chem. Chem. Phys., 2007, 9, 755
    DOI: 10.1039/B615318F

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