Synthesis, crystal structure, and computational studies of (E)-N, N′-ethylene-1,2-diamino-bis(N, N-dimethylbut-2-enamide)

The compound (E)-N, N′-ethylene-1,2-diamino-bis(N, N′-dimethylbut-2-enamide) was synthesized by a reaction between N, N′-dimethylacetoacetamide and ethylenediamine in a methanolic medium. The Schiff base compound was characterized by infrared (IR) spectroscopy, mass spectrometry (MS), thermogravimetry (TG), and single-crystal X-ray diffraction (XRD). The compound was crystallized in a triclinic crystal system with a space group of P-1. The amine functional group (-C=N-) was confirmed by the band at 1592 cm⁻¹ in its IR spectrum. The compound is thermally stable from 40 to 203 °C losing only 1.4% of its weight. The thermogram (TG) indicated the absence of any water of hydration or lattice water. It melts in the range of 166–169 °C. The compound exhibits keto-enol tautomerism with a zwitterionic structure. The non-covalent interactions (NCI) were studied by various computational methods such as Hirshfeld surface analysis, NCI plot, and scatter graph (RDG vs sign (λ₂)ρ). The major contributors to the Hirshfeld surface (HS) contacts are H---H (71%), O---H (11.7%), and C---H (12.2%). The crystal parameters are as follows: a = 6.3623(4) Å, b = 6.5585(4) (8) Å, c = 10.8135(7) Å, Z = 4, R1 = 0.0610, wR2 = 0.1447, α = 98.16 (4)°, β = 95.86(4)°, γ = 117.63(4)°.