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Article

Alkoxy-Functionalized Schiff-Base Ligation at Aluminum and Zinc: Synthesis, Structures and ROP Capability

1
Plastics Collaboratory, Department of Chemistry, University of Hull, Cottingham Road, Hull HU6 7RX, UK
2
Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China
3
Department of Chemistry, University of North Carolina Greensboro, Greensboro, NC 27402-6170, USA
*
Authors to whom correspondence should be addressed.
Academic Editor: Samuel Dagorne
Catalysts 2021, 11(9), 1090; https://doi.org/10.3390/catal11091090
Received: 14 August 2021 / Revised: 3 September 2021 / Accepted: 3 September 2021 / Published: 9 September 2021
(This article belongs to the Special Issue 10th Anniversary of Catalysts: Molecular Catalysis)
The Schiff-base compounds 2,4-di-tert-butyl-6-(((3,4,5-trimethoxyphenyl)imino)methyl)phenol (L1H), 2,4-di-tert-butyl-6-(((2,4,6-trimethoxyphenyl)imino)methyl)phenol (L2H), 2,4-di-tert-butyl-6-(((2,4-trimethoxyphenyl)imino)methyl)phenol) (L3H) derived from anilines bearing methoxy substituents have been employed in the preparation of alkylaluminum and zinc complexes. Molecular structure determinations reveal mono-chelate aluminum complexes of the type [Al(Ln)(Me)2] (L1, 1; L2, 2; L3, 3), and bis(chelate) complexes for zinc, namely [Zn(Ln)2] (L1, 5; L2, 6; L3, 7). All complexes have significant activity at 50 °C and higher activity at 100 °C for the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) with good control over the molar mass distribution (Mw/Mn < 2) and molecular weight. Complex 1 was found to be the most active catalyst, achieving 99% conversion within 18 h at 50 °C and giving polycaprolactone with high molecular weight; results are compared against aniline-derived (i.e., non-methoxy containing) complexes (4 and 8). Aluminum or zinc complexes derived from L1 exhibit higher activity as compared with complexes derived from L2 and L3. Complex 1 was also tested as an initiator for the copolymerization of ε-CL and glycolide (GL). The CL-GL copolymers have various microstructures depending on the feed ratio. The crosslinker 4,4′-bioxepane-7,7′-dione was used in the polymerization with ε-CL using 1, and well-defined cross-linked PCL was afforded of high molecular weight. View Full-Text
Keywords: Schiff base; organoaluminum; zinc; catalyst; polycaprolactone; copolymer; ring-opening polymerization; molecular structures Schiff base; organoaluminum; zinc; catalyst; polycaprolactone; copolymer; ring-opening polymerization; molecular structures
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MDPI and ACS Style

Zhang, X.; Chen, K.; Chicoma, M.; Goins, K.; Prior, T.J.; Nile, T.A.; Redshaw, C. Alkoxy-Functionalized Schiff-Base Ligation at Aluminum and Zinc: Synthesis, Structures and ROP Capability. Catalysts 2021, 11, 1090. https://doi.org/10.3390/catal11091090

AMA Style

Zhang X, Chen K, Chicoma M, Goins K, Prior TJ, Nile TA, Redshaw C. Alkoxy-Functionalized Schiff-Base Ligation at Aluminum and Zinc: Synthesis, Structures and ROP Capability. Catalysts. 2021; 11(9):1090. https://doi.org/10.3390/catal11091090

Chicago/Turabian Style

Zhang, Xin, Kai Chen, Melissa Chicoma, Kimberly Goins, Timothy J. Prior, Terence A. Nile, and Carl Redshaw. 2021. "Alkoxy-Functionalized Schiff-Base Ligation at Aluminum and Zinc: Synthesis, Structures and ROP Capability" Catalysts 11, no. 9: 1090. https://doi.org/10.3390/catal11091090

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