A new and efficient high-performance electrochemical glucose sensor based on a metallopolymer derived from a cobaltate (III) Schiff base complex

Through a simple and effective reaction of the cobalt (II) acetate tetrahydrate with a new ONO-tridentate Schiff base ligand (L1), which contains a thiophenyl group, a mono-anionic complex of formula: [{4-Th-C₆H₄-C(O)CH-C(CH₃)=N-C₆H₄-2-O}₂Co]^-[Bu₄N]⁺ (C1) was isolated. Spectroscopic tools (¹H and ¹³C NMR, FT-IR) and the crystal structure revealed that C1 consists of a mononuclear six-coordinate anionic Co(III) center with a pseudo-octahedral geometry, and one tetrabutylammonium counterion to satisfy the negative charge of the coordination entity [Co^III(L1)₂]^-. Electropolymerization of C1 produces a conductive metallopolymer deposit on fluorine-doped tin oxide (FTO) electrodes, which acts as an efficient glucose sensor, showing a linear amperometric response for glucose within a concentration range of 1.97 × 10 ⁻⁷ M to 3.88 × 10⁻⁶ M (R² = 0.993), limit of detection (LOD) of 9.27 × 10⁻⁷ M and limit of quantification (LOQ) of 9.24 × 10⁻⁶ M. This electrochemical sensor, which exhibit excellent reproducibility in the manufacturing process, was stable in environmental conditions and showed good reproducibility of the measurements for two weeks. In addition, the metallopolymer deposit was characterized by electrochemical techniques (cyclic voltammetry) and SEM microscopy.