Electrochemiluminescence properties and luminescence sensing of four novel polymers derived from 3-(pyrazin-2-yl)-1H-pyrazole-5-carboxylic acid

Abstract

On the basis of the 3-(pyrazin-2-yl)-1H-pyrazole-5-carboxylic acid (H₂L) ligand, four new polymers [Cu₂(L²⁻)₂] (1), [Zn₃(L²⁻)₂(H₂O)₄Cl₂]_n (2), [Pb(HL⁻)Cl]_n (3), and {[Ni(L²⁻)(H₂O)]·(H₂O)}_n (4) have been synthesized under solvothermal conditions. Polymer 1 possesses a discrete (0D) binuclear structure, which is further formed into a three-dimensional (3D) supramolecular structure by hydrogen bonding and π⋯π stacking interactions. Polymers 2 and 3 display one-dimensional (1D) infinite chain structures, which further extend into 3D supramolecular structures through hydrogen bonding interactions. Polymer 4 features two-dimensional (2D) layers which can form a 3D supramolecular architecture via interlayer hydrogen bonds. The ligand in the four polymers adopts different coordination modes for constructing versatile structures. Moreover, luminescence sensing study shows that polymer 2 is a promising luminescent sensor for the detection of Cu²⁺, Co²⁺ and Fe³⁺via drastic luminescence quenching in aqueous solution with high efficiency. The quenching constants K_SV for Cu²⁺, Co²⁺ and Fe³⁺ are 6.35 × 10³ M⁻¹, 8.70 × 10³ M⁻¹ and 1.62 × 10⁴ M⁻¹, respectively. What's more, 1–4 with electrochemical luminescence (ECL) properties show high intensity in N,N-dimethylformamide (DMF) solution and high thermal stability.