Synthesis, crystal structure, DFT calculations and Hirshfeld surface analysis of 3-butyl-2,6-bis(4-fluorophenyl)piperidin-4-one

The title compound, C₂₁H₂₃F₂NO, consists of two fluorophenyl groups and one butyl group equatorially oriented on a piperidine ring, which adopts a chair conformation. The dihedral angle between the mean planes of the phenyl rings is 72.1 (1)°. In the crystal, N—H...O and weak C—H...F interactions, which form R ² ₂[14] motifs, link the molecules into infinite C(6) chains propagating along [001]. A weak C—H...π interaction is also observed. A Hirshfeld surface analysis of the crystal structure indicates that the most significant contributions to the crystal packing are from H...H (53.3%), H...C/C...H (19.1%), H...F/F...H (15.7%) and H...O/O...H (7.7%) contacts. Density functional theory geometry-optimized calculations were compared to the experimentally determined structure in the solid state and used to determine the HOMO–LUMO energy gap and compare it to the UV–vis experimental spectrum.