Unveiling nonlinear optical behavior in benzophenone and benzophenone hydrazone derivatives

We systematically investigated the first-order molecular hyperpolarizability, a second-order nonlinear optical phenomenon of 185 organic compounds comprising both benzophenone and benzophenone hydrazone derivatives. We considered compounds with different combinations of electron donor groups -H, -F, -CH3, -Cl, -Br, OCH3, -NH2, -NHCH3, -NHC2H5, -N(CH3)2, and electron acceptor group -NO2 attached to the para positions R1 or R2 of the aromatic rings. The reported first-order molecular hyperpolarizability values were obtained by quantum-chemical calculations using semiempirical and density functional theory approaches in the gas phase. Our results reveal that BP-25 (R1 = NO2, R2 = N(CH3)2) and BPH-39 (R1 = N(CH3)2, R2 = NO2) exhibited the highest dynamic first-order molecular hyperpolarizability value of about \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text{23 }\times{\text{10}}<^>{\text{-30}}\text{ c}{\text{m}}<^>{\text{4}}\text{ }\text{statvol}{\text{t}}<^>{\text{-1}}$$\end{document}. These findings underline the potential of specific BP and BPH derivatives as candidates for photonic applications, particularly for developing second harmonic generation crystals.