Structural studies of (E)-2-(benzylidene)-1- tetralone derivatives: Crystal structures and Hirshfeld surface analysis

Crystal structures are reported from data collected at 100 K of (E)-2-(X-benzylidene)-1-tetralone (2: X=3-O₂N; 3: X=4-O₂N; 5: X=4-HO; 6: X=4-Me₂N; 7: 4-NC), (E)-2-(X-benzylidene)-6-MeO-1-tetralone, 8, and (E)-2-(X-benzylidene)-5-MeO-1-tetralone 9. Also reported herein are the Hirshfeld surface calculations for these compounds as well as those of (E)-2-(X-benzylidene)-1-tetralone (1: X=H; 4: X=4-MeO), whose structures were previously reported. The molecules are not planar as shown by the dihedral angles of 45.66(5)-69.78(5)° between the phenyl groups and by the puckered cyclohexenyl rings. A common feature of the molecular conformations is the C-H···O1(carbonyl) intramolecular hydrogen bond. The carbonyl oxygen atom plays significant roles in the interactions in all compounds baring compound 8. However, there is no consistent set of intermolecular interaction in this group of compounds. Intermolecular interactions present in each compound are some of the O-H···O, C-H···A (A=O, N or π), A-O···π (A=C or N) and π···π interactions. The only compound exhibiting a classical O-H···O hydrogen bond is compound 5. C-H···π interactions are found in all compounds, and while π···π interactions are present in compounds 2, 3, 7 and 9, no consistent type of stacking arrangement is shown. The Hirshfeld surface calculations, while generally concurring with the intermolecular interactions indicated by PLATON analyses, also reveal short interactions, which fall below the PLATON cut-off parameters.