Redox-Active Ru(II)-Bipyridinedicarboxamide-Based Polysiloxane Complexes as Photoluminescent Chemosensors for Heavy Metal Ions and pH

Polymer–metal complexes (PMCs) based on poly(2,2′-bipyridine-4,4′-dicarboxamide- co -polydimethylsiloxanes) with ruthenium(II) fragments were obtained by two different approaches, including (i) polymer ligand modification by [RuBpy 2 ] 2+ and [RuPhen 2 ] 2+ (Bpy = 2,2′-bipyridine, Phen = 1,10-phenantroline) incorporation and (ii) cross-linking via complexation of the polysiloxane ligand with RuCl 3 . The polymer ligands and corresponding PMCs were characterized by 1 H and 13 C{ 1 H} NMR, FTIR, UV–vis, EDX, and photoluminescence (PL) spectroscopies. All obtained PMCs provide phosphorescence at λ em = 602–670 nm and PL lifetimes up to τ 0 = 1.26 μs. The electrochemical and self-healing behavior of the PMCs was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and tensile tests, respectively. The PMCs exhibit redox properties showing up to three well-defined redox waves attributed to ligand-centered processes (at E 1/2 from −1.5 to −1.1 V), Ru I /Ru II (at E 1/2 ≈ −0.9 V), and Ru II /Ru III (at E 1/2 from +1.1 to +1.3 V) transformations. The cross-linked PMCs with a wide range of elongation at break (up to 800%) and self-healing efficiency up to 91% at 100 °C were synthesized. The cross-linked PMCs can act as flexible, stretchable, PL, and self-healing sensors toward heavy metal ions (Cu 2+, Hg 2+, and Pb 2+ ), Cl –, and pH by decreasing their PL intensity.