Abstract
The synthesis and characterization of water-soluble copolymers containing N,N-dimethylacrylamide (DMAM) and a vinylic monomer containing an Iridium(III), Ir(III), complex substituted with the quinoline-based unit 2-(pyridin-2-ylo)-6-styrene-4-phenylquinoline (VQPy) as ligand are reported. These copolymers were prepared through pre- or post-polymerization complexation of Ir(III) with the VQPy units. The first methodology led to copolymer P1 having fully complexed VQPy units, whereas the latter methodology allowed the preparation of terpolymers containing free and Ir(III)-complexed VQPy units (copolymer P2). The optical properties of the copolymers were studied in detail through UV-Vis and photoluminescence spectroscopy in aqueous solution. It is shown that the metal-to-ligand charge transfer (ΜLCT) emission is prevailing in the case of P1, regardless of pH. In contrast, in the case of terpolymer P2 the MLCT emission of the Ir(III) complex is combined with the pH-responsive emission of free VQPy units, leading to characteristic pH-responsive color changes under UV illumination in the acidic pH region.
Highlights
Transition-metal complexes are well-known for their ability to achieve high-efficiency phosphorescence because they can harvest both singlet and triplet excitons
The monomer 2-(pyridin-2-ylo)-6-styrene-4-phenylquinoline) (VQPy) was according to literature procedures [62], through a Friedländer reaction followed by a Suzuki synthesized according to literature procedures [62], through a Friedländer reaction cross-coupling reaction
We focused on thecomplexation optical properties, especially emission, of the novel namely preormostly post-polymerization of Ir(III)
Summary
Transition-metal complexes are well-known for their ability to achieve high-efficiency phosphorescence because they can harvest both singlet and triplet excitons Motivated by this property, cyclometalated complexes based on metal ions such as Ru(II), Rh(I), Pt(II), and Ir(III) have been largely investigated [1–4]. The development of water-soluble luminescent Ir(III) complexes is valuable for biological and biochemical applications such as bioprobes for cell imaging or their use as indicators to determine parameters such as pH, temperature, or oxygen. To this end, the ligands may be functionalized with hydrophilic groups [13,14,32–37] or the counter ions of cationic cyclometalated Ir(III) complexes may be adequately chosen to sustain water-solubility [14,38–40]. The covalent attachment of Ir(III) complexes onto a polymeric chain, using water-soluble polymers such as poly(N-isopropylacrylamide), poly(N-vinylpyrrolidone), and polyethyleneglycols, has been applied [41–50]
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