Insights into supramolecular assembly formation of diethyl aryl amino methylene malonate (DAM)derivatives assisted via non-covalent interactions

The crystal structures of four derivatives of diethyl 2-(((aryl)amino)methylene)malonate (DAM)have been studied by single crystal X-ray diffraction. The molecular structures of all the four derivatives were found to be in co-planar conformation. The detailed analysis of molecular conformation in four derivatives reveals the presence of a common strong intramolecular N–H⋯O hydrogen bonding, forming a ring of graph-set motif S<inf>1</inf> ¹ (6). The effect of chloro and nitro substitution on their relative strengths of hydrogen bonding are analyzed here. Particularly, in compound 1, additional intramolecular hydrogen bonding between –NO<inf>2</inf> and N–H was observed that results in the formation of another six-membered chelate ring. On the other hand in case of compound 3, we have observed type-I Cl⋯Cl interaction for the first time in this class of compounds. Further, Hirshfeld surface has been generated that is mapped with d<inf>norm</inf> shape index and curvedness to summarize the weak interactions and examine the molecular shapes in all four derivatives. Effect of nitro (1 and 2)and chloro (3 and 4)substitution on the C⋯H, N⋯O and C⋯O interaction is highlighted in molecular contour and 2D fingerprint plots.