Ring opening polymerization ofd,l-lactide and ε-caprolactone catalysed by (pyrazol-1-yl)copper(ii) carboxylate complexes

Divambal Appavoo, Lara C. Spencer, Ilia A. Guzei, Carlos J. Gómez-García, Juanita L. van Wyk, James Darkwa

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


1,2-Bis{(3,5-dimethylpyrazol-1-yl)methyl}benzene (L) reacts with [Cu(OAc)2] and C6H5COOH, 4-OH-C6H4COOH, 2-Cl-C6H4COOH and (3,5-NO2)2-C6H3COOH to afford the copper complexes [Cu2(C6H5COO)4(L)2] (1), [Cu2(4-OH-C6H4COO)4(L)2] (2), [Cu2(2-Cl-C6H4COO)4(L)2]n(3) and [Cu{(3,5-NO2)2-C6H3COO}2L]n(4) which are characterised by IR, mass spectrometry, elemental analyses, and X-ray crystallography. The structural data revealed two geometries that are adopted by the complexes: (i) paddle wheel in1,2·7H2O,3and (ii) regular chains in3and4. Magnetic studies show strong antiferromagnetic couplings in the paddle wheel complexes and a weak antiferromagnetic coupling in the monometallic chain one. Catalysis studies performed with these complexes (1-4) showed that they initiate ring opening polymerization (ROP) of ε-caprolactone (ε-CL) under solvent-free conditions andd,l-lactide in toluene at elevated temperatures. Polycaprolactone (PCL) and poly(d,l-lactide) (PLA) obtained from the polymerization reactions are of low molecular weights (858 for PCL and 602 Da for PLA for initiator1) and polydispersity indices (typically 2.16 for PCL and 1.64 for PLA with1as the initiator). End group analysis of the polymers, determined by MALDI-ToF MS, indicates that the polymers have benzoate, hydroxyl, methoxy and cyclic end groups.

Original languageEnglish
Pages (from-to)13475-13485
Number of pages11
JournalRSC Advances
Issue number22
Publication statusPublished - 12 Apr 2021

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering


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