A cobalt(ii) coordination polymer with 6-aminonicotinate and 1,2-bis(4-pyridyl)ethane as a new electrochemical sensor for determination of dopamine

Abstract

Dopamine (DA), a typical and representative catecholamine, is crucial for medical treatment and clinical analysis because it is an essential neurotransmitter. Electrochemical detection is widely used to monitor neurotransmitters associated with disease because of its rapid response, ease of use, and high sensitivity. Challenges to be overcome include the sensitivity and selectivity of modified electrodes for electrocatalysis of biological molecules and their electrochemical detection in the presence of other interfering species. A new electrochemical sensor for determination of dopamine, based on a cobalt(II) coordination polymer with 6-aminonicotinate (6-aminopyridine-3-carboxylate, 6-NH₂nic) and 1,2-bis(4-pyridyl)ethane (1,2-bpe), {[Co(1,2-bpe)₂(H₂O)₂](6-NH₂nic)(NO₃)·4H₂O}_n (1), is reported. Compound 1 is a 6-aminonicotinate and nitrate salt of a one-dimensional polymeric {[Co(1,2-bpe)₂(H₂O)₂]²⁺}_n cation, in which the cobalt(II) ion is octahedrally coordinated by four N,N′-bridging 1,2-bis(4-pyridyl)ethane ligands and two water molecules in the trans position. The adjacent cobalt(II) ions are connected by two N,N′-bridging 1,2-bis(4-pyridyl)ethane ligands in the syn conformation, leading to an infinite one-dimensional polymeric chain extending along the [0 1 0] direction. The glassy carbon electrode (GCE) modified with 1 showed excellent electroanalytical activity towards the oxidation of dopamine in KCl solution (pH 6.0), enabling the electrochemical determination of dopamine using square wave voltammetry (SWV). The proposed method for dopamine determination is simple, rapid and based on a wide linear concentration range of 0.01–1.00 mmol dm⁻³, with a lower detection limit of 0.4 μmol dm⁻³, an excellent sensitivity of 0.065 μA (μmol dm⁻³)⁻¹, good selectivity and high durability.