A theoretical investigation into the cooperativity effect involving anionic hydrogen bond, thermodynamic property and aromaticity in Cl−⋯benzonitrile⋯H2O ternary complex

The cooperativity effects involving the O/CH⋯Cl− anionic H-bonding interactions in Cl−⋯benzonitrile⋯H2O ternary complexes are investigated by using the B3LYP and MP2(full) methods with the 6-311++G(2d,p) and aug-cc-pVTZ basis sets. The thermodynamic cooperativity and the influence of the H-bond cooperativity effect on the aromaticity of benzonitrile ring are also evaluated. The result shows that the influence of the O/CH⋯Cl− anionic H-bonding interaction on the OH⋯N or CH⋯O interaction is more pronounced than that of the latter on the former. The cooperativity effect appears in the linear complex while the anti-cooperativity effect is found in the cyclic system. The enthalpy change is the major factor driving the cooperativity in forming the linear ternary complex while entropy change turns into the favorable factor in forming the cyclic system. The aromaticity characterized by nucleus-independent chemical shifts (NICS) is weakened and the bond dissociation energy (BDE) of the CCN bond increase upon the ternary-complex formation. The cooperativity effect (Ecoop.) correlates well with Rc (NICS(1)ternary/NICS(1)binary), RBDE(CCN) (BDE(CCN)ternary/BDE(CCN)binary) and the change of chemical shift ΔΔδ (Δδternary − Δδbinary), respectively.