Highly efficient,catalyst‐free,one‐pot,pseudo five‐component synthesis of novel pyrazoline‐containing Schiff bases,metal complexes formation and computational studies via DFT method

In this study, a green and high yielding synthesis of novel pyrazoline‐containing Schiff bases via a one‐pot pseudo five‐component condensation reaction under catalyst‐free conditions in EtOH at room temperature is described. Initially, the reaction of 1,1‐bis(methylthio)‐2‐nitroethylene (BMTNE), with NH₂NH₂.H₂O is used for situ preparation of 1,1‐dihydrazino‐2‐nitroethylene (DHNE). Then, wide varieties of aldehydes are added to the mixture to afford the desired products good to excellent yields. This synthetic route is presented with several unique merits such as simplicity in operation and workup, readily presented starting materials, and high functional group tolerance. Additionally, the stoichiometric complex formation of these Schiff bases as ligand (L) with various metal ions Mn(OAc)₂, Cu(OAc)₂ and Zn(OAc)₂] in general molecular formula ML] is examined via Job's method. Subsequently, theoretical analysis of the product is accomplished using density functional theory (DFT) calculations. According to the frontier molecular orbital (FMO) analysis, it is found that the aryl group linked to the imine bond contributes as an electron donor in the ligand–metal complex.