Synthesis, Crystal Structure, DFT Calculations and Hirshfeld Surface Analysis of 3-Chloro-3-methyl-r(2),c(6)-bis(p-methoxyphenyl)piperidin-4-one

Abstract

The title compound, C20H22ClNO3, [common name: 3-chloro-3-methyl-r(2),c(6)-bis(p-methoxyphenyl)piperidin-4-one] crystallizes in the P21/c space group with unit cell parameters a = 13.4020(11) A, b = 7.7888(5) A and c = 18.1721(14) A, β = 108.250(9)°, Z = 4. The central piperidin-4-one ring (N1/C1–C5), adopts a slightly distorted chair conformation and an equatorial orientation of all its substituents except for chlorine which is axially located. The dihedral angle between the mean planes of the two phenyl rings is 47.9(4)° and between the piperidin-4- one ring and pendant phenyl rings is 68.8(2)° (C6–C11) and 73.1(6)° (C13–C18), respectively. Crystal packing is stabilized by weak C–H⋯O intermolecular interactions forming chains along the b-axis. Additional weak Cg–π interactions between nearby phenyl rings are also observed. A comparison of these bond lengths and angles within the crystal with Density Functional Theory (DFT) geometry optimized calculations at the B3LYP/6-31+G (d) level has been determined. Hirshfeld surface analysis for determining the molecular shape and visually analyzing the intermolecular interactions in the crystal structure employing 3D molecular surface contours and 2D fingerprint plots gave enrichment ratios for H⋯H, O⋯H, Cl⋯H and C⋯H contacts compared to C–C, Cl⋯Cl and C⋯Cl contacts indicating a higher propensity for O–H interactions to form in this crystal. Electronic transitions have also been predicted by DFT Molecular Orbital calculations and compared to experimental absorption spectra. Molecular orbital diagrams provide visual representations of the top level molecular orbital surfaces in the compound.