Highly Active Homoleptic Zinc and Magnesium Complexes Supported by Constrained Reduced Schiff Base Ligands for the Ring-Opening Polymerization of Lactide

Tanyawan Pongpanit; Thonthun Saeteaw; Phongnarin Chumsaeng; Pongsakorn Chasing; Khamphee Phomphrai

doi:10.1021/acs.inorgchem.1c02382

Highly Active Homoleptic Zinc and Magnesium Complexes Supported by Constrained Reduced Schiff Base Ligands for the Ring-Opening Polymerization of Lactide

Inorg Chem. 2021 Nov 15;60(22):17114-17122. doi: 10.1021/acs.inorgchem.1c02382. Epub 2021 Oct 4.

Authors

Tanyawan Pongpanit¹, Thonthun Saeteaw¹, Phongnarin Chumsaeng¹, Pongsakorn Chasing¹, Khamphee Phomphrai¹

Affiliation

¹ Department of Materials Science and Engineering, School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology, Wangchan, Rayong 21210, Thailand.

PMID: 34605644
DOI: 10.1021/acs.inorgchem.1c02382

Abstract

New homoleptic zinc and magnesium complexes containing constrained reduced Schiff base ligands based on substituted 7-hydroxy-1-indanone were successfully synthesized and used as a catalyst for the polymerization of lactide. The ligands contain a side arm having different basicity because dimethylamino, pyridyl, and furfuryl groups are shown to greatly affect the polymerization rates. The homoleptic zinc complex containing constrained reduced Schiff base ligands and a dimethylamino side arm was highly active, giving a 92% conversion of l-lactide in 3 min using [LA]:[Zn]:[BnOH] = 500:1:2 at room temperature. The polymerization is pseudo-first-order dependent on the LA concentration. Well-controlled and living behavior of the zinc complex was observed and demonstrated in the preparation of stereodiblock and triblock copolymers of l-, d-, and rac-lactide in a one-pot sequential synthesis with a predictable block length, block sequence, and narrow dispersity rapidly in 10 min. Stereocomplex formation was observed for PLA made sequentially from 100 l-LA, 100 rac-LA, and 100 d-LA having a high T_m of up to 220 °C.