Hirshfeld Surface Analysis and Energy Framework for Crystals of Quinazoline Methylidene Bridged Compounds

The crystal structures of 4-(3,4-dimethoxyphenylethylamino)-methylidene-2,3,4,10-tetrahydro-1H-pyrido[2,1-b]-quinazolin-10-one (1) and 4-(3,4-methylene-dioxyphenylethylamino)-methylidene-2,3,4,10-tetrahydro-1H-pyrido[2,1-b]-quina-zolin-10-one hydrochloride (2) were studied by single crystal X-ray diffraction. Their molecular and crystal structures are described in the context of intra- and inter-molecular interactions and of stereoisomerism. The crystallographic study established mixed E, Z configuration about the C4=C12 bond for (1) and E configuration about the C4=C12 bond for (2). For molecular crystals, Hirshfeld surface analyses may provide insight into intermolecular interactions, and energy framework analyses allow one to quantify different contributions to the overall energy. These analyses were performed to pinpoint intermolecular interactions in (1) and (2). According to our results, the molecules are associated with intra- and intermolecular hydrogen bonds, C-H···$π$ and $π$-stacking interactions. The three-dimensional Hirshfeld surface analyses and two-dimensional fingerprint plots revealed that the structures are dominated by H···H, H···C/C···H and H···O/O···H contacts. The intermolecular energy analysis confirmed a significant contribution of dispersion to the stabilization of molecular packings in (1) and (2)