Quantum chemical exploration of linear and nonlinear optical characteristics in C-acylated pyrazoles

The present work deals with the linear and nonlinear optical properties (the dipole moment, polarizability, total hyperpolarizability, electric field–induced second harmonic generation, and hyper-Rayleigh scattering first hyperpolarizability) of five C-acylated pyrazoles as essential compounds with specific photophysical properties. Based on density functional theory at different functionals (B3LYP, PBE0, BVP86, CAM-B3LYP, and ωB97X-D), the properties have been successfully calculated and analysed extensively to limelight on the nonlinear optical activity. The obtained results show a high total first hyperpolarizability \({\beta }_{\text{tot}}\) ${\beta }_{\text{tot}}$ up to 1240 a.u. and low energy gap \({E}_{\text{g}}\) $E_{\text{g}}$ less than 2.7 eV. An inverse relationship has been obtained between the \({\beta }_{\text{tot}}\) ${\beta }_{\text{tot}}$ and \({E}_{\text{g}}\) $E_{\text{g}}$ . The calculated \({E}_{\text{g}}\) $E_{\text{g}}$ values confirm that charge occurs within the C-acylated pyrazoles. This study may provide new ways to utilize these analogues as NLO materials.