Crystal Growth, Optical, Thermal, DFT and Z-Scan Studies of Imidazolium Hydrogen Fumarate Crystal for Nonlinear Optical Applications

Organic imidazolium hydrogen fumarate (IHF) crystals are grown using the slow evaporation method. The IHF has triclinic crystal structure. The ¹H NMR spectrum has five chemical shifts for the IHF crystal. The band at 3155 cm⁻¹ in IR occurs due to the presence of O─H stretching vibration of the IHF molecule. The bandgap value of the IHF crystal is determined to be 4.6 eV. The intense violet emission band is noted at 361 nm. The IHF crystal has thermal stability value of 179 °C. Hirshfeld surface is used to find out the different intermolecular interactions of the IHF crystal. The HOMO–LUMO energy gap is determined to be 4.70 eV. The hydrogen atoms have positive potential in the MEP analysis. The high stabilization energy of 56.81 kcal mol⁻¹ is noticed for π*(C1─N7) → π*(C2─C3) interaction. The third-order NLO susceptibility (χ⁽³⁾) of the IHF is 2.08934 × 10⁻⁹ esu.