Crystal structure and theoretical studies of two π-conjugated fused-ring chalcones: (E)-1-(anthracen-9-yl)-3-(9-ethyl-9H-carbazol-3-yl)prop-2-en-1-one and (E)-1-(anthracen-9-yl)-3-[4-(9H-carbazol-9-yl)phenyl]prop-2-en-1-one

The title chalcones, C31H23NO and C35H23NO, were synthesized via Claisen–Schmidt condensation reactions. Both structures were solved and refined using single-crystal X-ray diffraction data and optimized at the ground state using the density functional theory (DFT) method with the B3LYP/6-311++G(d,p) level. In the crystals, π–π interations and weak C—H...O and C—H...π interactions are observed. The effect of these intermolecular interactions in the solid state can be seen by the difference between the experimental and theoretical optimized geometrical parameters. The structures have also been characterized by UV–Vis spectroscopy. The smallest energy gaps of 2.86 and 2.96 eV enhance the nonlinear responses of such molecular systems. Hirshfeld surface analyses and 2D (two-dimensional) fingerprint plots were used to quantify the intermolecular interactions present in the crystal, indicating that these are the most important contribution to the crystal packing