Molecular Structure, Linear, and Nonlinear Optical Properties of Piperazine-1,4-Diium Bis 2,4,6-Trinitrophenolate: A Theoretical Investigation

We theoretically investigated molecular structure, vibrational analysis, linear and nonlinear optical properties of the piperazine-1,4-diium bis 2,4,6-trinitrophenolate by employing density functional theory at several levels. To understand their linear and nonlinear optical behavior, dipole moment, polarizability, and first order hyperpolarizability β have been calculated and analysed in details. The hyper-Rayleigh scattering first hyperpolarizability, the electric field–induced second harmonic generation, and the depolarization ratios are the targeted quantities. The groups NO2, NH2, C=C, C-N, and phenolic 'O' atom were identified using theoretical vibrational analysis. The calculated of highest occupied molecular orbital, lowest unoccupied molecular orbital, and their energy gap are also presented. Global chemical reactivity descriptors and the three-dimensional molecular electrostatic potential were studied and discussed. Calculations highlight that 1°) predicted geometrical parameters show very good correlations with the corresponding experimental ones. 2°) A good correlation between the calculated and experimental vibration frequencies was also observed. 3°) A direct relationship between the energy gap and β has been obtained. 4°) The variation in β calculated confirmed the nonlinear optical activity of the studied piperazine. This work will help people understand the nonlinear optical properties of piperazine based molecules and provide guidance for the rational design of molecules with excellent optoelectronic properties.