| Abstract |
A 1:1 reaction of 8-(dihydroimidazolyl)quinoline (abbreviated as L) with MCl2 center dot 2H(2)O (M = Co-II, Ni-II, Cu-II, Zn-II) conducted in EtOAc (for Zn-II and Cu-II) or MeOH (Ni-II and Co-II) at 50 degrees C for 10 min provided the respective air- and shelf-stable [MCl2L] complexes (94-96\%). The catalytic activity of these well-defined species was evaluated in L-lactide ring-opening polymerization (ROP) that was conducted in the presence of 2-hydroxyethylmethacrylate (HEMA) as a nucleophilic initiator. The biocompatible zinc(II) complex was found to be more catalytically active in ROP compared to the other three complexes as well as SnOct(2), a common reference catalyst. The zinc(II)-catalyzed ROP also gives the macromolecular product with the lowest polydispersity index (1.2). The applicability of the HEMA-terminated PLA, prepared in the presence of the [ZnCl2L] complex, was demonstrated when PLA was converted into amphiphilic copolymer PLA-PEG via the thiol-ene click reaction. The PLA-PEG copolymer was shown to form nanospheres (calculated mean diameter 95 +/- 10 nm) characterized by low particle size distribution. This - along with anticipated lower toxicity of [ZnCl2L] traces in the polymer - makes these nanospheres potentially applicable as vehicles for intravenous drug delivery. (C) 2019 Elsevier Inc. All rights reserved. |
