American Chemical Society, Journal of Organic Chemistry, 18(79), p. 8599-8606, 2014
DOI: 10.1021/jo501251s
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The influence of multiple substituents (F, CH3, NO2, CN, Cl, OH and NH2) on the C-H…π interaction in benzene-ethylene complex was investigated using the estimated CCSD(T) method and complete basis set limit. The results were compared with our earlier reported complexes of benzene-acetylene and benzene-methane, thus completing the sp, sp2 and sp3 series of C-H donors. The stabilization energy values for multiple flouro-substituted benzene-ethylene complexes are found to be very close to those of the multiple flouro-substituted benzene-methane complexes. Expectedly, the stabilization energies for the multiple methyl-substituted benzene-ethylene complexes lie between those of the multiple methyl-substituted benzene-methane and benzene-acetylene complexes. Energy decomposition analysis using the DFT-SAPT method predicts the dispersion energy to be dominant, similar to the benzene-methane complexes. For the symmetrically disubstituted complexes (-OH, -Cl, -NH2, -CN and -NO2), additional C-H…X interaction was observed possibly due to the angular orientation of the ethylene molecule. Multidimensional correlation analysis between the electrostatic, dispersion and exchange-repulsion with the C-H…π interaction distance (r), Hammett constant (σ) and the molar refractivity (MR) revealed strong correlation between dispersion energy and the C-H…π interaction distance (r) as well as molar refractivity (MR).