Synthesis of miktoarm star copolymer Ru(II) complexes by click-to-chelate approach

Abstract

A series of AB2-, ABC-, (AB)2-, A2B 2- and ABCD-type miktoarm copolymer Ru(II) complexes was synthesized by a stepwise chelating method, which involved the first-step chelating reaction of Ru(II)(DMSO)4Cl2 with a polymer-substituted 2-(1H-1,2,3-triazol-4-yl)pyridine (tapy) or 2,6-bis(1H-1,2,3-triazol-4-yl) pyridine (bitapy) ligand to produce a stable polymer Ru(II) mono-complex, and a second-step chelating reaction of the polymer Ru(II) mono-complex with another tapy or bitapy ligand to afford the miktoarm copolymer Ru(II) complexes. In order to synthesize them, the polymer-substituted tapy and bitapy ligands were first prepared by the click reaction of azido-terminated polymers with 2-ethynylpyridine and 2,6-diethynylpyridine, respectively. The azido-terminated polystyrene (PS) and poly(n-butyl acrylate) (PBA) were prepared by the atom-transfer radical polymerizations of styrene and n-butyl acrylate using ethyl 2-bromoisobutyrate as the initiator, followed by the substitutions of their end bromines with an azido group, respectively. The azido-terminated poly(n-hexyl isocyanate) was prepared by the living coordination polymerization of n-hexyl isocyanate using dichloro(cyclopentadienyl)(6-azidohexyloxy)titanium that was prepared by mixing 6-azido-1-hexanol with trichloro(cyclopentadienyl) titanium before the polymerization. The azido-terminated poly(styrene oxide) and poly(ε-caprolactone) were synthesized by the controlled/living ring-opening polymerizations of ε-caprolactone using diphenyl phosphate as the catalyst and of styrene oxide using the phosphazene base of t-Bu-P 4 as the catalyst, respectively, in which 6-azido-1-hexanol was used as the initiator. © 2013 The Society of Polymer Science, Japan (SPSJ) All rights reserved.