Reinvestigation of the crystal structure, vibrational spectroscopic studies and DFT calculations of 4, 4′-bipyridinium dinitrate: An efficient SHG material for electro-optic devices

Abstract

4,4′-Bipyridinium dinitrate (BPDN) has the potential to be a candidate material for nonlinear optical devices. In this work, the crystal and molecular structure of this molecule were reinvestigated using single-crystal X-ray diffraction, and its FT-IR and the UV–Vis spectra were recorded. The compositional ratio of BPDN was investigated using energy-dispersive X-ray analysis (EDX) and the thermal stability of the grown crystal was studied. The results indicate that the title compound (BPDN) belongs to the orthorhombic crystal system with the noncentrosymmetrical space group Fdd2. The nonlinear optical (NLO) behaviour of the BPDN crystal was examined by the Kurtz and Perry powder method and was found to be 0.931 times greater than that of KDP. This high hyperpolarizability of BPDN is attributed to the different electronic delocalization and supramolecular architecture. The π–π electron delocalization led to the increase in the hyperpolarizability of BPDN, which was approximately 65 times greater than that of urea. Hirshfeld analyses were performed to identify the diverse intermolecular and intramolecular interactions that are responsible for the stabilization of the title crystal.