Vibrational versus electronic first hyperpolarizabilities of mono- and disubstituted benzenes: An Ab initio coupled Hartree-Fock investigation

Static electronic and vibrational longitudinal first hyperpolarizabilities (β_L ^ν(0) and β_L ^ν(0)) of a series of mono- and disubstituted benzenes were calculated at the Hartree-Fock 6-31G level by using coupled Hartree-Fock and the double harmonic oscillator aproximations, respectively. Althogh the β_L ^ν(0)/β_L ^ν(0) ratio is slightly larger than unity and rather constant with respect to the substituent(s), it turns out, for the monosubstituted compounds, that the variationss of β_L ^ν(0) upon substitution can be most accounted for by the mesomeric effects, whereas for β_L ^ν(0), the inductive effects are also of importance.