Synthesis of zinc complexes bearing pyridine derivatives and their application of ε-caprolactone and L-Lactide polymerization

A series of pyridine and polypyridine-zinc complexes were synthesized, and their application in ε-caprolactone and l-lactide polymerization was studied. In ε-caprolactone polymerization, zinc complexes bearing 1,10-phenanthroline derivatives exhibited a higher polymerization rate than did diethyl zinc (2–10 times). In l-lactide polymerization, zinc complexes bearing 1,10-phenanthroline derivatives exhibited a considerably higher polymerization rate than did diethyl zinc (2–220 times). According to density functional theory results, the ortho-hydrogens of polypyridine ligand can co-activate the carbonyl group of monomers with zinc metal center to increase the catalytic activity of zinc catalysts.