Synthesis, structural-spectral characterization and theoretical studies of Pyridinium-4-carbohydrazide (2R,3R)-2,3-dihydroxybutanedioate

A new cocrystal Pyridinium-4-carbohydrazide (2R,3R)-2,3-dihydroxybutanedioate (PCDHB) has been synthesized and single crystals grown by slow evaporation method. The structure of the new cocrystal was determined by single crystal X-ray diffraction studies. It crystallizes in the non-centrosymmetric orthorhombic space group P 2(1) 2(1) 2(1) with lattice parameters of a = 7.8791(5) angstrom, b = 15.163(1) angstrom, c = 19.8952(13) angstrom. The compound has been further characterized by FTIR and powder X-ray diffraction studies. The dielectric and thermal studies as well as the UV-Vis NIR spectral and photoluminescence studies have been carried out. The optical band gap has been estimated to be 3.0 eV. Thermal analysis revealed that the cocrystal is stable up to a temperature of 162.7 degrees C. The compound shows 86% transparency in the entire visible and UV-Vis region with a lower cut-off wavelength of 310 nm. The title compound exhibits a second harmonic generation efficiency which is 2.23 times higher than the commercial KDP crystal. DFT studies have been carried out on the optimized crystal structure which revealed a wide network of intermolecular hydrogen bonding. Natural bond orbital analysis, Mulliken atomic charges studies have also been carried out to understand the electronic transitions, charge distribution and the stability of the cocrystal. (C) 2021 Elsevier B.V. All rights reserved.