Crystal structure, DFT calculation, Hirshfeld surface analysis and energy framework study of 6-bromo-2-(4-bromophenyl)imidazo[1,2-<i>a</i>]pyridine

Abstract

The title imidazo[1,2-<i>a</i>] pyridine derivative, C₁₃H₈Br₂N₂, was synthesized <i>via</i> a single-step reaction method. The title mol-ecule is planar, showing a dihedral angle of 0.62 (17)° between the phenyl and the imidazo[1,2-<i>a</i>] pyridine rings. An intra-molecular C-H⋯N hydrogen bond with an <i>S</i>(5) ring motif is present. In the crystal, a short H⋯H contact links adjacent mol-ecules into inversion-related dimers. The dimers are linked in turn by weak C-H⋯π and slipped π-π stacking inter-actions, forming layers parallel to (110). The layers are connected into a three-dimensional network by short Br⋯H contacts. Two-dimensional fingerprint plots and three-dimensional Hirshfeld surface analysis of the inter-molecular contacts reveal that the most important contributions for the crystal packing are from H⋯Br/Br⋯H (26.1%), H⋯H (21.7%), H⋯C/C⋯H (21.3%) and C⋯C (6.5%) inter-actions. Energy framework calculations suggest that the contacts formed between mol-ecules are largely dispersive in nature. Analysis of HOMO-LUMO energies from a DFT calculation reveals the pure π character of the aromatic rings with the highest electron density on the phenyl ring, and σ character of the electron density on the Br atoms. The HOMO-LUMO gap was found to be 4.343 eV.