Synthesis of an Asymmetric Imine/bis(pyrazolyl)alkane Ligand



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The field of coordination chemistry has a variety of applications, both biological and industrial. Some notable products include pharmaceutical compounds like L-DOPA (used as a treatment for Parkinsonï¾’s disease) and cisplatin (an anticancer drug), and consumer-grade products like fibers and plastics (through polymerization of ethylene and propylene). To that end, the use of metal coordination complexes is a crucial part of ensuring efficient reactions. In this experiment, we explore the synthesis of nonsymmetrical ligands using an imine/bis(pyrazolyl)alkane as a base for the production of new bimetallic coordination complexes. A successful synthesis was achieved using 2,6-diformyl-4-tert-butylphenol followed by a two-step di-substitution reaction of aniline and bis-(3,5-dimethylpyrazolyl)methanone. Product identity was confirmed by proton NMR. Additionally, it was found that by using an unsubstituted aniline, and in the absence of acid, synthesis of the asymmetric ligand could be achieved with close to 99% yield and in relatively high purity. Furthermore, under scaled-up conditions, the reaction had similar yield and purity when compared to the small-scale reaction. These results show promise, as large amounts of ligand can be made for future metal ion chelation. The next step in our research is to use our imine/bis(pyrazolyl) ligand for hetero- and homobimetallic substitutions using main group elements, like zinc and lithium.