Crystal structures, DFT studies and UV–visible absorption spectra of two anthracenyl chalcone derivatives

The crystal structures of (E)-1-(anthracen-9-yl)-3-(3H-indol-2-yl)prop-2-en-1-one, C(25)H(17)NO, and (E)-1-(anthracen-9-yl)-3-[4-(di­methyl­amino)­naphthalen-1-yl]prop-2-en-1-one, C(29)H(23)NO, are reported. In each case the anthracene ring system and pendant ring system are almost perpendicular to each other [dihedral angles = 75.57 (7)° and 70.26 (10)°, respectively]. In the extended structures, weak N—H⋯O, C—H⋯O and C—H⋯π inter­actions influence the centrosymmetric crystal packing. Density functional theory calculations were carried out using a 6–311 G++(d,p) basis set and the calculated structures are in good agreement with the crystal structures. The compounds were also characterized by UV–Vis absorption spectroscopy and the smallest (HOMO–LUMO) energy gaps of 2.89 and 2.54 eV indicate the enhanced non-linear responses (inter­molecular charge transfers) of these systems.