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, OCH_3, -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 \(\text{23 }\times{\text{10}}^{\text{-30}}\text{ c}{\text{m}}^{\text{4}}\text{ }\text{statvol}{\text{t}}^{\text{-1}}\). These findings underline the potential of specific BP and BPH derivatives as candidates for photonic applications, particularly for developing second harmonic generation crystals.