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

The title chalcones, C31 H23 NO and C35 H23 NO, 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 inter-ations and weak C-H⋯O and C-H⋯π inter-actions are observed. The effect of these inter-molecular inter-actions 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 mol-ecular systems. Hirshfeld surface analyses and 2D (two-dimensional) fingerprint plots were used to qu-antify the inter-molecular inter-actions present in the crystal, indicating that these are the most important contribution to the crystal packing.