In this paper, we describe the synthesis of a new di-hydro-2H-pyridazin-3-one derivative. The mol-ecule, C18H16N2O, is not planar; the benzene and pyridazine rings are twisted with respect to each other, making a dihedral angle of 11.47 (2)°, and the toluene ring is nearly perpendicular to the pyridazine ring, with a dihedral angle of 89.624 (1)°. The mol-ecular conformation is stabilized by weak intra-molecular C-H⋯N contacts. In the crystal, pairs of N-H⋯O hydrogen bonds link the mol-ecules into inversion dimers with an R 2 2(8) ring motif. The inter-molecular inter-actions were investigated using Hirshfeld surface analysis and two-dimensional (2D) fingerprint plots, revealing that the most important contributions for the crystal packing are from H⋯H (56.6%), H⋯C/C⋯H (22.6%), O⋯H/H⋯O (10.0%) and N⋯C/C⋯N (3.5%) inter-actions.
Keywords: Hirshfeld surface analysis; crystal structure; pyridazine; pyridazine derivative; pyridazinone.