Frontiers in Chemistry (Apr 2019)

Synthesis and Characterization of N,N,O-Tridentate Aminophenolate Zinc Complexes and Their Catalysis in the Ring-Opening Polymerization of Lactides

  • Wei-Yi Lu,
  • Kuo-Hui Wu,
  • Hsuan-Ying Chen,
  • Hsuan-Ying Chen,
  • Chu-Chieh Lin

DOI
https://doi.org/10.3389/fchem.2019.00189
Journal volume & issue
Vol. 7

Abstract

Read online

A series of aminophenolate ligands with various pendant groups and associated ethyl Zn complexes were synthesized and studied as catalysts for the ring-opening polymerization (ROP) of lactides (LAs). The thiophenylmethyl group (L4ZnEt) increased the catalytic activity more than the benzyl group (L1ZnEt) did, and 2-fluorobenzyl (L3ZnEt) and 2-methoxybenzyl (L2ZnEt) groups had the opposite effect. In addition, the LA polymerization mechanism proved by Nuclear Magnetic Resonance and Density Function Theory was that LA was attracted by H···O bond of an α-hydrogen of the LA molecule and the phenoxyl oxygen of the catalyst. After the dissociation of amino group from the Zn atom, the benzyl alcohol initiated LA without replacing the ethyl group of Zn complex. It is the first case where the ethyl group is regarded as a ligand and cannot be replaced by benzyl alcohol, and this information is very important for the mechanism study of ROP.

Keywords