Experimental and DFT Structure Investigation of Pyridine Interaction with Dihalogen Molecules, UV-Visible, Cyclic Voltammetry and Hirshfeld Surface Analysis

Different density functional theory (DFT) approaches (CAM-B3LYP, B3LYP, B97-D3, and M06-2X) were performed to determine the structures and the interaction energies of the formed complexes between pyridine and a series of dihalogen molecules IY (Y = F, Cl, Br, I) and were matched to the experimental XRD data. A combination of computational and experimental methods is reported to investigate the nature of the halogen bonding (XB) between P-y-I-2 and Py-ICl. The rise in interaction energy of Py-IY was justified by the increase in electronegativity going from iodine to fluorine. Besides, halogen bond interactions were quantified using Hirshfeld surface analysis. The latter revealed the existence of H center dot center dot center dot I and H center dot center dot center dot Cl intermolecular bonds, with major contributor for Py-I2 and Py-ICl, respectively. The accordance between the experimental and theoretical UV spectra demonstrates the reliability of the M06-2X/6-311 + G(d,p): LANL2DZ level of theory employed herein. Experimentally, halogen bonding in P-y-I-2 and P-y-ICl complexes was examined via UV-vis spectral analysis and cyclic voltammetry.