New Brønsted–Lowry acid Co(II) complexes: Synthesis, characterization, and investigation of electrochemical application for sensing of salbutamol

In recent years, the employment of transition metal complexes for working electrode surface modification for sensor fabrication has become an area of research direction. Based on this, in this study, three Co(II) complexes: Co(phen)Cl₂ (CoC₁₂H₈N₂Cl₂) (C1), and Brønsted–Lowry acids Co(phen)(HTA)Cl (CoC₁₆H₁₃N₂O₆Cl)(C2), and Co(phen)(HTA)₂ (CoC₂₀H₁₈N₂O₁₂)(C3) were synthesized and characterized using various techniques such as UV–Vis, FT-IR, ICP OES, TGA, DTA, pXRD as well as electrolytic conductivity, and acid-base property analysis. C and C3 were found polycrystalline whose size falls within the nano range of 50 and 51 nm, respectively. The synthesis was intended to get materials for voltammetrically modifying glassy carbon electrodes for the determination of salbutamol. Salbutamol is a short-acting β₂ adrenergic receptor agonist that is applied for opening the medium and large airways in the lungs and eventually treats asthma among other problems. The electrochemical application of the synthesized materials was studied by fabricating through electropolymerization of C1, C2, and C3 on glassy carbon electrodes. The poly(C1)/GCE, poly(C2)/GCE, and poly(C3)/GCE) revealed effective surface area is 0.174 cm², 0.183 cm², and 0.281 cm², respectively, and electrochemical catalysis of the materials increased with the number of the tartrate. The Rct values are 5686, 242, 216, and 185 Ω cm², while the C_dl values are 9.93 × 10⁻⁸, 5.35 × 10⁻⁶, 1.25 × 10⁻⁵, and 2.72 × 10⁻⁵, for bare GCE, poly(C1)/GCE, poly(C2)/GCE and poly(C3)/GCE, respectively. Similarly, the rate of charge transfer (k°) increased significantly on the modified electrode compared to the bare GCE. Salbutamol demonstrated a single well-shaped irreversible oxidative peak at the modified electrodes in the ascending order of poly(C1)/GCE, poly(C2)/GCE, and poly(C3)/GCE when compared to a bare GCE.