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摘要
The stabilisation energies of the crystal structures of 1,3-dithiole-2-thione-4-carboxyclic acid center dot center dot center dot I-2 and DABCO center dot center dot center dot I-2 complexes determined by the CCSD(T)/CBS method are very large and exceed 8 and 15 kcal mol(-1), respectively. The DFT-D method (B97-D3/def2-QZVP) strongly overestimates these stabilisation energies, which support the well-known fact that the DFT-D method is not very applicable to the study of charge-transfer complexes. On the other hand, the M06-2X/def2-QZVP method provides surprisingly reliable energies. A DFT-SAPT analysis has shown that a substantial stabilisation of these complexes arises from the charge-transfer energy included in the induction energy and that the respective induction energy is much larger than that of other non-covalently bound complexes. The total stabilisation energies of the complexes mentioned as well as of those where iodine has been replaced by lighter halogens (Br-2 and Cl-2) or by hetero systems (IF, ICH3, N-2) correlate well with the magnitude of the sigma-hole (V-s,V-max value) as well as with the LUMO energy. The nature of the stabilisation of all complexes between both electron donors and X-2 (X = I, Br, Cl, N) systems is explained by the magnitude of the s-hole but surprisingly also by the values of the electric quadrupole moment of these systems. Evidently, the nature of the stabilisation of halogen-bonded complexes between electron donors and systems where the first non-zero electric multipole moment is the quadrupole moment can be explained not only by the recently introduced concept of the s-hole but also by the classical concept of electric quadrupole moments.
- 出版日期2014
