Exploring Polymorphism in Quinoline‐4‐Carbaldoxime: Experimental Validation and Computational Insights into Hydrogen Bonding and Structural Variations

• Published in: ChemistrySelect (Weinheim) 2024-10, Vol.9 (37), p.n/a
• Main Authors: Tarai, Arup, Tarai, Swarup Kumar, Sutradhar, Dipankar, Bhowmick, Somnath, Moi, Sankar Ch, Nath, Bhaskar
• Format: Article
• Language: English
• Subjects: Computational analysis; Hydrogen bonding; Polymorphs; Supramolecular assembly
• ISSN: 2365-6549; 2365-6549
• DOI: 10.1002/slct.202403906

This study identifies and characterizes a second polymorph (Poly‐II) of quinoline‐4‐carbaldoxime (HQ), isolated from an acetone‐acetonitrile mixture. Poly‐II was compared to the previously known Poly‐I using PXRD, DSC, IR, and Raman spectroscopy. Poly‐I forms a 1D supramolecular assembly, whereas Poly‐II exhibits a 2D assembly with additional hydrogen bonds. Hirshfeld surface analysis reveals the presence of different non‐covalent interactions in Poly‐I and Poly‐II, and atom‐in‐molecule (AIM) analysis identifies their strength. AIM analysis, along with Espinosa's relation, was used to calculate the strength of O─H···N and C─H···N interactions in Poly‐I and Poly‐II. The values are −30.0 and −6.17 kJ/mol for Poly‐I, whereas the values for Poly‐II are −36.18 and −3.66 kJ/mol. The plane wave periodic DFT calculations determined the lattice energies of Poly‐I and Poly‐II to be −1.52 and −1.53 eV, respectively, indicating that both polymorphs have comparable stability. The crystal parameters of Poly‐I and Poly‐II obtained from theoretical simulations and the experiment are comparable, indicating the similar stability of Poly‐I and Poly‐II. Computational simulations confirmed experimental data, showing both polymorphs have similar stability and melting points despite different unit cell volumes. Structural elucidation and comparative analysis on two packing polymorphs of quinoline‐4‐carbaldoxime (HQ) by investigating hydrogen bond strength, melting point analysis, and lattice energy calculation. The PXRD, FT‐IR, Raman, and DSC experiments are performed to distinguish the two polymorphs. In addition, the geometry optimization, AIM, and Hirshfeld surface analysis are accomplished to identify different weak interactions present in both polymorphs.