Structure-directing interactions in the crystals of tertiary butyl carbazate based imines: A combined experimental and theoretical investigation

A convenient and facile synthesis of (E)-Tert-butyl 2-(4-methoxybenzylidine) hydrazine carboxylate(a), (E)Tert-butyl-2-benzylidene hydrazine carboxylate(b), (E)-Tert-butyl-2-(2-nitrobenzylidene) hydrazine carboxylate (c), (E)-Tert-butyl-2-(2-bromobenzylidene) hydrazine carboxylate(d), (E)-tert-butyl 2-(4-chorobenzylidene) hydrazine carboxylate(e) and (E)-Tert-butyl-2-(4-nitrobenzylidene) hydrazine carboxylate(f) were accomplished by refluxing t-butyl carbazate with an appropriate aldehyde in ethanol. In-depth spectroscopic methods combined with X-ray crystallography and theoretical calculations were used to characterize and identify interactions between and within different groups of t-butyl carbazate based imines(a-e). Compound a, b and e crystallizes in orthorhombic crystal system with Pca21space group, while as compound c, d and f crystallizes in monoclinic crystal system with P21/c space group. For compounds a-f the dominant structure-directing motif is a pairwise O & sdot;& sdot;& sdot;H interaction between carbonyl oxygens with hydrazine hydrogen and aromatic hydrogens in the form of NH...O = C and CH...O = C. In addition to this, Pi stacking interactions along with CH...Pi interactions and other short contacts are the defining aspect of crystal packing. Their solid-state behavior was also studied using Hirshfeld surfaces. Hirshfeld surface analysis was also applied to discern the intermolecular interactions, highlighting the significance of hydrogen bonding, van der Waals forces, and the influence of specific substituents. Crystal packing motifs were investigated with the aid of Hirshfeld surface fingerprint plots. Using the quantum theory of atoms in molecules and non-covalent interaction methods, hydrogen bonds and other weak interactions were examined. The key factor forming the hydrogen-bond system is the ability of hydrazine and carboxylate groups to donate and take protons, which ultimately leads to the establishment of interaction networks.