3 years ago

Synthesis and polymerization kinetics of ε-caprolactone and ʟ-lactide to low molecular weight polyesters catalyzed by Zn(II) and Cu(II) N-hydroxy-N,N′-diarylformamidine complexes

Synthesis and polymerization kinetics of ε-caprolactone and ʟ-lactide to low molecular weight polyesters catalyzed by Zn(II) and Cu(II) N-hydroxy-N,N′-diarylformamidine complexes
Discrete Zn(II) and Cu(II) complexes have been synthesized by using N-hydroxy-N,N′-diarylformamidine ligands: N-hydroxy-N,N′-bis(2,6-diisopropylphenyl)formamidine (L1), N-hydroxy-N,N′-bis(2,6-dimethyl)formamidine (L2), N-hydroxy-N-(2-methoxyphenyl)-N′-(2,6-diisopropylphenyl)formamidine (L3), and N-hydroxy-N-(2-methoxyphenyl)-N′-(2,6-dimethylphenyl)formamidine (L4). Reaction of ligands L1L4 with either ZnOAc2·2H2O or CuOAc2·2H2O in aqueous ethanol gave mononuclear Zn(II) or Cu(II) complexes [Zn-(L1)2] (1), [Zn-(L2)2] (2), [Zn-(L3)2] (3) and [Zn-(L4)2] (4), or [Cu-(L1)2] (5), [Cu-(L2)2] (6), [Cu-(L3)2] (7) and [Cu-(L4)2] (8), respectively, with high yields of up to 84%. All the complexes were characterized by elemental analysis, IR, NMR and mass spectroscopy. The molecular structures of complexes 3 and 7 were determined by single crystal X-ray diffraction analyses. The Zn(II) center in complex 3 exhibited a distorted tetrahedral geometry while in complex 7, the Cu(II) center had a square planar geometry with near C 2 symmetry. In both structures, the coordination sites are occupied by imino N- and hydroxyl O-donor atoms from the chelating ligands. All complexes showed catalytic activity and exhibited well-controlled living polymerization process in ring-opening polymerization of ε-caprolactone and l-lactide in the presence of benzyl alcohol co-initiator. The molecular weights were found to be low ranging from 1855 to 3999 Da for polycaprolactone (PCL) and up to 1720 Da for polylactic acid (PLA). The Zn(II) catalysts were found to be more active than Cu(II) catalysts with complex 2 (k app = 0.1751 h−1) being the most active.

Publisher URL: www.sciencedirect.com/science

DOI: S027753871730606X

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.