Synthesis, structural characterization and Hirshfeld surface analysis of NLO active 3-hydroxypyridinium 2,4-dinitrophenolate single crystals

Single crystals of 3-hydroxypyridinium 2,4-dinitrophenolate (I) and 4-hydroxypyridinium 2,4-dinitrophenolate (II) was harvested under slow evaporation conditions. The yellow block crystals formed by O–H⋯O and N–H⋯O hydrogen bonding that made contacts through the cation and anion was characterized by single-crystal X-ray diffraction, infrared spectrum, diffuse reflectance spectrum, thermogravimetric and Hirshfeld surface analysis. Crystal (I) packed orthorhombic crystal system with acentric P2 1 2 1 2 1 space group and (II) packed in monoclinic system with centric P2 1 / c space group. Intra-/intermolecular hydrogen bonds and weak van der Waals forces construct the supramolecular network in the crystal packing. The bandgap energy was estimated using diffuse reflectance spectral data by the application of the Kubelka–Munk algorithm. The non-linear optical response is examined by the Kurtz–Perry technique gave the result that the efficacy of crystal (I) is ~ 4 times greater than that of reference KDP. TG/DTA analysis reveals the thermal pattern of the compounds. Fingerprint plot used to locate and analyse the percentage contribution of hydrogen bonding interactions. First-order molecular hyperpolarizability calculated using theoretical calculations shows a significant microlevel nonlinearity in both cases.