Synthesis and characterization of random and block copolymers with pendant rhenium diimine complexes by controlled radical polymerization

Abstract

We report the polymerization of rhenium-containing methacrylates by atom transfer radical polymerization. The structure of the monomer was confirmed by X-ray crystallography, which showed the bulkiness of the metal-complex moiety. The rhenium complexes were polymerized in the presence of copper(I) bromide, 1,1,4,7,7-pentamethyldiethylenetriamine, and methyl 2-bromopropionate. They were copolymerized with methyl methacrylate in different monomer ratios. An ABA triblock copolymer was also synthesized with poly(methyl methacrylate) as the macroinitiator. When 2,2Ј-bipyridine was used as the ligand for the copper catalyst in the polymerizations, it underwent a ligand exchange process with the iminopyridine ligand in the monomer. The neutral rhenium complex in the homopolymers and copolymers could be converted into ionic forms by the replacement of the chloride with an imidazole ligand, and the solubility of the resulting ionic polymers was greatly enhanced. The photosensitizing properties of the doped and undoped polymer films were investigated by the measurement of the photocurrent response under an externally applied electric field. The photoconductivities of the polymers were approximately 10 Ϫ12 -10 Ϫ13 ⍀ Ϫ1 cm Ϫ1 . The experimental quantum efficiencies were simulated with Onsager's theory, and they showed that the initial quantum yield and thermalization distance were 10 Ϫ3 and 1.7 nm, respectively. Transmission electron microscopy showed that the rhenium complexes aggregated to form domains with dimensions of approximately 20 -30 nm.

Transition Metal-Catalyzed Living Radical Polymerization: Toward Perfection in Catalysis and Precision Polymer Synthesis

“…Fluorinated segments is statistically incorporated into the side chains of linear polymers via copper-catalyzed polymerization of a pendant-fluorinated methacrylate and MMA (FR- 31 ) , or St (FR- 32 ) (Figure ). Additionally, copper-catalyzed system efficiently performs statistical copolymerization of bulky pendant-bearing monomers including a bulky hostasol moiety for FR- 33 , FR- 34 , a metal complex (FM- 75 ) for FB- 35 , and bulky/rigid biphenyl fluorine-bearing methacrylates (FM- 90 /FM- 99 ) for FB- 36 . The hostasol-tagged polymers (FR- 33 , FR- 34 ) obtained with FI- 54 or FI- 55 are applied to bioconjugation to efficiently work as fluorescently labeled polymers.…”

Photogenerated avenues in macromolecules containing Re(i), Ru(ii), Os(ii), and Ir(iii) metal complexes of pyridine-based ligands

“…The copolymerization of MMA with different Re(I) complex/ MMA ratios was demonstrated as well as the synthesis of an ABA triblock copolymer with PMMA, as macroinitiator. 175 Scheme 22 Schematic representation of poly(arylene ethynylene) (PPE) architectures containing Re(I) complexes. 186 The neutral Re(I) complex in the homopolymers and copolymers was further converted into an ionic form by replacing the chloride ligand by an imidazole ligand, thereby significantly enhancing the solubility of the resulting ionic polymers.…”

Rhenium(I) N-Heterocyclic Carbene Complexes in Photoinitiating Systems for Polymerization upon Visible Light: Development of Photosensitive Resins for 3D and 4D Applications

“…On the other hand, the photochemistry of metal carbonyls has been the subject of extensive studies as well, and the topic was covered by several excellent reviews. − The excited-state properties of rhenium­(I) tris -carbonyl complexes of general formula [Re­(CO) 3 (N^N)­L] n + , where N^N is an α , α ’-diimine ligand such as 2,2′-bipyridine or 1,10-phenanthroline and related derivatives and L = halogen (for n = 0) or a monodentate neutral ligand (for n = 1), were intriguing; for instance, a substituted phosphine or pyridine was first recognized in the mid-1970s. , Since then, photoactive Re­(I) complexes have attracted much interest. − Previous studies have shown that the [Re­(CO) 3 (N^N)­L] n+ class of complexes are emissive from low-lying triplet excited states with a metal-to-ligand charge transfer ( 3 MLCT) character with sometimes admixed triplet ligand-centered ( 3 LC) manifold, namely 3 LC/ 3 MLCT, and are highly sensitive to environmental rigidity and changes. ,− Furthermore, depending on the nature of both the coordinated ancillary and diimine ligands, these complexes may display bright photoluminescence either in fluid solution at room temperature or at low temperature in glassy matrices. , Nevertheless, the photochemistry and photophysics of rhenium complexes is largely dominated by compounds bearing diimine type of ligands, ,− , whereas congeners bearing NHC ligands are much less explored to date. The first examples of such a family were reported in 2011 by Massi, and only a few other related compounds have been reported since, which mainly explored the coordination and optical properties of complexes featuring imidazolylidene and benzimidazolylidene scaffolds. − …”