Structural investigations of halogen substituted 1,4-dihydropyridine derivatives: Crystallographic and computational studies

Single crystal structure solution and refinement have been carried out on 1,4-dihydropyridine derivative molecules, namely, 4-(4‑chloro-phenyl)-2,6-dimethyl-1, 4-dihydropyridine-3,5-dicarboxylic acid bis-[(2-chlorophenyl)amide] and 4-(4-fluoro-phenyl)-2,6-dimethyl-1, 4-dihydropyridine-3,5-dicarboxylic acid bis-[(2-chlorophenyl)amide]. Final refinement values, of [I > 2σ(I)] (all data) were refined as 0.0608 (0.0768) and 0.0595 (0.0696) for M-Cl and M-F. Hirshfeld surfaces analysis mapped dnorm surfaces, shape index, curvedness and hydrogen bonding in both the molecules and major relative contributions to the percentage of Hirshfeld surface area for the various intermolecular contacts were calculated. DFT studies using Quantum ESPRESSO were carried out by transformation of the conventional monoclinic unit cell to the primitive unit cell converted back to the original monoclinic cell to compare with the experimental data. The NBO analysis implemented in Gaussian was used to know intermolecular force between two molecular units and to obtain the stabilization energies from donors to acceptors in M-Cl and M-F. The natural localized molecular orbital (NLMO) analysis was also performed to capture the intermolecular delocalization interactions of NBOs.