Evaluation of weak noncovalent interactions in three regioisomeric benzylideneaniline derivatives: An integrated crystallographic and theoretical approach

A new benzylideneaniline derivative, N-(4-nitrobenzylidene)-4'-fluoroaniline (I), was synthesized by a condensation reaction between 4-nitrobenzaldehyde and 4-fluoroaniline. The crystal structure of I was analyzed and compared with two regioisomeric benzylideneaniline derivatives, viz.N-(3-nitrobenzylidene)-4'-fluoroani- line (II) and N-(4-nitrobenzylidene)-2'-fluoroaniline (III), reported in the literature. The crystal structures of I-III were subjected to evaluation of their interatomic interactions in the crystal using Hirshfeld surface (HS) analysis and Coulomb-London-Pauli-PIXEL (CLP-PIXEL)and DFT calculations. The investigation reveals that the crystal packing of I-III was stabilized by the weak C-H & sdot;& sdot;& sdot;O, C-H & sdot;& sdot;& sdot;F and C-H & sdot;& sdot;& sdot;pi interactions. Intermolecular interaction energies for different molecular pairs in the crystal packing of I-III, as well as the total lattice energies were quantified. The total lattice energies of the three regioisomeric benzylideneanilines (I-III) are compared and the dipole moment (mu), the polarizability (alpha tot) and the first-order hyperpolarizability (beta tot) of I-III were computed using the M06-2X/cc-pVTZ level of theory.