科研之友
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摘要
The cooperativity effects between H-bonding and Na+center dot center dot center dot pi or Na+center dot center dot center dot sigma interactions in Na+center dot center dot center dot benzonitrile center dot center dot center dot H2O complexes were investigated using the B3LYP and MP2(full) methods with 6-311++G(2d,p) and aug-cc-pVTZ basis sets. The thermodynamic cooperativity and the influence of this cooperativity on aromaticity was evaluated by nucleus-independent chemical shifts (NICS). The results showed that the influence of the Na+center dot center dot center dot sigma or Na+center dot center dot center dot pi interaction on the hydrogen bond is more pronounced than that of the latter on the former. The cooperativity effect appeared in the Na+center dot center dot center dot sigma interaction complex while the anti-cooperativity effect tended to be in the Na+center dot center dot center dot pi system. The change in enthalpy is the major factor driving cooperativity. Thermodynamic cooperativity is not in accordance with the cooperativity effect evaluated by the change of interaction energy. The ring aromaticity of is weakened while the bond dissociation energy (BDE) of the C-CN bond increases upon ternary complex formation. The cooperativity effect (E-coop) correlates with R-c (NICS(1)(ternary)/NICS(1)(binary)) and Delta Delta delta (Delta delta(ternary) - Delta delta(binary)) involving the ring and C N bond, as well as RBDE(C-CN) [BDE(C-CN)ternary/BDE(C-CN)binary], respectively. AIM (atoms in molecules) analysis confirms the existence of cooperativity.
