Structural studies of (E)-2-(benzylidene)-2,3-dihydro-1H-inden-1-one derivatives: crystal structures and Hirshfeld surface analysis

Crystal structures are reported of (E)-2-(4-hydroxybenzylidene)-2,3-dihydro-1Hinden-1-one, 1, (E)-2-(4-dimethylaminobenzylidene)-2,3dihydro-1H-inden-1-one, 2, (E)-2-(4-cyanobenzylidene)2,3-dihydro-1H-inden-1-one, 3, and monoclinic-(E)2-( 3-nitrobenzylidene)-2,3-dihydro-1H-inden-1-one, monoclinic-4, all from data collected at 100 K and (E)-2-(4hydroxy-3,5-dimethylbenzylidene)-2,3-dihydro-1H-indan1-one, 6, from data collected at 299 K. An earlier triclinic form of 4 has been reported. Also reported herein are the Hirshfeld suface calculations for these five compounds, as well as that of 2-(4-methoxybenzylidene)-2,3-dihydro1H-inden-1-one, 5, whose crystal structure has been previously reported. The three rings in each of the compounds, 1-4 and 6, are essentially planar, including the five-membered ring containing a formally hydridized sp(3) atom. The molecules exhibit slight deviations from overall planarity as shown by the dihedral angles, > 8.15(6)degrees between the 2,3-dihydro-1H-inden-1-one fragments and the phenyl fragments. The main intermolecular interactions in compounds 1 and are classical O-H center dot center dot center dot O1(carbonyl) hydrogen bonds. The carbonyl oxygen atom in compounds 1-4 are involved in non-classical C-H center dot center dot center dot O intermolecular hydrogen bonds. Intermolecular C-H center dot center dot center dot pi interactions are present in 2, 3 and 6, while pi center dot center dot center dot pi are present in 2-4 and 6. As noted in the structure determinations of these compounds, different pi center dot center dot center dot pi motifs are possible. The Hirshfeld surface calculations, while generally concurring with the intermolecular interactions indicated by PLATON analyses, also reveal significant interactions, which fall below the PLATON radar.