Structural and anionic effects of microcrystalline Zn-CPs on 4-nitrophenol sensing performances

Coordination polymers (CPs: [ZnL₃] (X)₂ , L = trans-1,4-bis(imidazolyl)-2-butene; X^- = BF₄ ^-, ClO₄ ^-, NO₃ ^-) allow for detection of the 4-nitrophenol (4-NP) oxidation process by enhanced electrochemical signals. Electrochemical measurement is a highly sensitive method providing much evidence of chemical reactions on an electrode surface. In the present study, we designed and synthesized, with reference to X-ray diffraction data and by spectroscopic analyses, new 3D coordination structures containing imidazolyl donors and zinc(ii). The presence of microcrystals [ZnL₃] (BF₄)₂ on the working electrode enhanced the redox signals. Therefore, we propose a simple catalytic process that can explain these results and clarify the influence of anions that constitute CP materials used to improve electrochemical detection applications. The CP materials were characterized by nuclear magnetic resonance (NMR), infrared spectroscopy (IR), thermogravimetric (TG) analyses, single crystal X-ray diffraction (SC-XRD), and electrochemical analyses.