Ring-opening polymerization of lactides and ε-caprolactone catalyzed by Zn(II) aryl carboxylate complexes supported by 4-pyridinyl schiff base ligands.

Synthesis and catalytic studies of aryl carboxylate Zn (II) complexes is reported. Reaction of substituted ()--phenyl-1-(pyridin-4-yl)methanimine with a methanolic solution of Zn(CHCOO) and substituted aryl carboxylate co-ligands gave heteroleptic Zn(II) complexes; [Zn(CHCOO)()] (), [Zn(CHCOO)()] (), [Zn (4-F-CHCOO)()] (), [Zn(CHCOO)()] (), [Zn(CHCOO)()] (), [Zn (4-F-CHCOO)()] (), [Zn(CHCOO)()] (), [Zn(CHCOO)()] (), [Zn (4-F-CHCOO)()] (). The molecular structures of complexes and are dinuclear with the zinc atom in complex adopting a distorted trigonal bipyramidal geometry in a bi-metallacycle while complex is square pyramidal where all four benzoate ligands bridge the zinc metals in a paddle wheel arrangement. All complexes successfully initiated mass/bulk ring-opening polymerization (ROP) of ϵ-caprolactone (ϵ-CL) and lactides (LAs) monomers with or without alcohol co-initiators at elevated temperatures. Complexes , and containing the unsubstituted benzoate co-ligands were the most active in their triad; with complex being the most active ( ) of 0.3450 h. The physicochemical properties of the polymerization products of -lactide and -lactide in toluene revealed melting temperatures (T) between 116.58 °C and 188.03 °C, and decomposition temperatures between 278.78 °C and 331.32 °C suggestive of an isotactic PLA with a metal capped end.