Synthesis and structural studies of 4-[(5-methoxy-1H-indole-3-yl)-methylene]-3-methyl-isoxazole-5-one by X-ray crystallography, NMR spectroscopy, and DFT calculations

► A merocyanine dye with isoxazolone nucleus was synthesized. ► The dye crystallizes in the P21/n space group with four molecules per unit cell. ► The hydrogen bonds and π⋯π aromatic stacking interactions exist in the crystal. ► MEP shows the hydrogen bonds are formed between the positive and negative regions. ► NMR spectra obtained by DFT/GIAO are in good agreement with the experimental values.