Polymers of ε-Caprolactone Using New Copper(II) and Zinc(II) Complexes as Initiators: Synthesis, Characterization and X-Ray Crystal Structures

Abstract

Five of six new Zn(II) and Cu(II) complexes were active in the ring-opening polymerization (ROP) of ε-caprolactone (CL) under solvent-free conditions, producing polycaprolactones (PCLs) of high crystallinity with molecular weights between 22,900 and 38,700 g mol−1 and decomposition temperatures above 260 °C. 1H NMR analysis demonstrated that the PCLs obtained were mainly linear, having hydroxymethylene groups at the chain ends. The results obtained indicated a significant improvement in terms of the ratio of monomer:initiator compared to related Cu(II) and Zn(II) complexes. In addition, the structures of the complexes 1 and 4 were determined by single-crystal X-ray diffraction. The synthesis and full characterization of all complexes are described in this paper.

Sensitive and Profitable Electrochemical Detection of Uric Acid in the Presence of Dopamine with a Novel Carbon Paste Electrode Decorated with a Copper(II) Complex

“…The electrochemical properties of the carbon paste surface decorated with Cu C were investigated via EIS and CV using 10.0 mmol L À 1 K 4 Fe(CN) 6 in 10.0 mmol L À 1 KCl as the test electrolyte. Moreover, the presence of metals ions, such as copper ions, was assessed via EDS.We previously studied the synthesis and characterization of copper(II) complexes derived from azole and they have received considerable attention due to their low cost, easy preparation, air-stable and electroactive properties [24][25][26][27] In the CV measurement for the ferri/ferrocyanide couple with CPE and Cu C /CPE ( Figure 1A), the anodic and cathodic peak potentials were observed at almost the same potential values of 0.66 V and À 0.20 V, respectively, with a ΔE of 0.81 V, indicating a quasi-reversible redox reaction. However, the anodic and cathodic peak currents increased by almost 30.6 % and 55.1 %, respectively, with the CPE decorated with Cu C .…”

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

“…29 One metal of growing interest is copper, which although has not been investigated as much as metals like zinc, shows interesting properties such as biocompatibility and good electron transfer ability that make Cu-based complexes good candidates for ROP catalysis. [30][31][32] The catalytic activity of organometallic complexes is largely determined by the ligands attached to the metal centre. For instance, backbiting reactions can be eliminated by using a suitable sterically bulky ligand that provides some amount of steric barrier around the metal centre.…”

“…For instance, backbiting reactions can be eliminated by using a suitable sterically bulky ligand that provides some amount of steric barrier around the metal centre. Several ligands have been explored to obtain the optimum catalytic performance of metal complexes; including amino-phenolate, [33][34][35] salicylaldimine, 32 formamide, 36,37 pyrazolyl, 30,[38][39][40][41] and benzoimidazolyl. [42][43][44] Pyrazole and its derivatives constitute an important group of Ndonor ligands that have been used because of their attractive coordination chemistry.…”

“… 29 One metal of growing interest is copper, which although has not been investigated as much as metals like zinc, shows interesting properties such as biocompatibility and good electron transfer ability that make Cu-based complexes good candidates for ROP catalysis. 30–32 …”

Application of Diethylzinc/Propyl Gallate Catalytic System for Ring-Opening Copolymerization of rac-Lactide and ε-Caprolactone

“…Zinc salts, such as lactate [13], aceturate, or L-prolinate [27] were found to be active catalysts for ROP of LLA. Organic zinc complexes were also successfully used as initiators/catalysts for the homopolymerization of LA [28,29,30,31], CL [32,33] or copolymerization of CL, and LA [34,35,36]. Zinc-based catalysts may be a viable alternative to SnOct 2 due to low toxicity and programmable polymer chain microstructure.…”