Synthesis, molecular structural, optical, thermal and third harmonic nonlinear optical analysis of Piperazine-1,4-diium bis(2-carboxy-6-nitrobenzoate) tetrahydrate single crystal

Abstract

Structure and molecular interactions of the title molecular salt (NPP) were established by X-ray diffraction. The elucidated structure model assigns centrosymmetric triclinic arrangement for the molecules. Molecular packing was established through robust O–H⋯O, N–H⋯O and C–H⋯O hydrogen bond network revealing infinite chains, sheets and spiral ladder patterns. The molecular patterns were abridged through C–H … π and π – π linkages expressing several S and R graph set motifs. Single crystals of NPP with defined morphology were grown by the method of slow evaporation from solution from 1: 1 mixed solvent of methanol and water. FT- IR, FT - Raman spectra reinforced the functional groups and with NMR spectra, the protonated-deprotonated nature of the title molecule. UV–visible, Urbach plot, photoluminescence and fluorescence spectral profiles endorsed the electronic transitions and photophysical properties of NPP. Z-scan profile in the closed and open aperture modes was deployed to estimate the magnitude of the third-order nonlinear optical constants. Thermogravimetry coupled with Differential Scanning Calorimetry (DSC) declare the optimal thermal stability of the material till 71.8 °C.