Facile Synthesis, Crystal Structure, Spectral Characterization, Quantum Chemical Calculations, and Hirshfeld Surface Analysis of 5-Chloro-3-Methoxy-4-Hydroxybenzaldehyde

This article deals with synthesis, growth, structure, and characterization of 5-chloro-3-methoxy-4-hydroxybenzaldehyde (5CMHBA or 5-chlorovanillin) single crystals. A facile one-pot method is employed for the chlorination of vanillin using N-chlorosuccinimide. After chlorination, the single crystals of 5CMHBA are grown by slow evaporation solution growth technique. Grown crystals are subjected to single crystal X-ray diffraction (SXRD), Fourier Transform Infrared (FTIR), and Thermogravimetric-Differential Thermal Analysis (TG-DTA). 5CMHBA crystallizes in the tetragonal crystal system with the space group P4(2)/n. Vibrational characteristics are studied using FTIR. Further, thermal studies of the crystal are carried out using simultaneous TG-DTA thermal analyzer. The molecular structure and its intermolecular interactions are studied by applying time-dependent density functional theory (TD-DFT) using Gaussian 09 program and Hirshfeld surface analysis. A lesser energy gap of the 5CMHBA compared to that of vanillin shows the high reactivity of the molecule. Dipole moment, polarizability, and hyper-polarizability are calculated in the molecular level and found to have greater polarizability than vanillin and also higher in order than that of standard urea molecule. This reveals the suitability of the molecule for nonlinear optical applications. The intermolecular interactions and porosity are analyzed and compared with vanillin and its polymorphs by Hirshfeld surface analysis.