Structure, Characterizations and Corrosion Inhibition of New Coordination Polymer Based on Cadmium Azide and Nicotinate Ligand

Abstract

Green crystals of the coordination polymer (CP) [CdN₃(en)(n)], 1, was obtained by reaction of CdSO₄ · 5H₂O with ethyl nicotinate (en) in the presence of NaN₃. The structure of the CP 1 was characterized by elemental analysis, IR, ¹H-NMR, UV-Visible and X-ray single crystal analysis. The ORTEP plot of CP 1 consists of [(Cd)₄(N₃)₄(en)₄(n)₄] structure exhibiting 14-atom V-shaped cyclic configuration, which contains 8-atoms ring [(Cd)₄(N₃)₄]. The structure of CP 1 creates 1D-chain where the cyclic structures are connected by two nicotinate ligands (n). The chains are extended in three directions forming 3D-network structure via extensive H-bonds. The CP 1 was tested as corrosion inhibitor for copper in 1 M HCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results of polarization indicated that CP 1 acts as mixed type inhibitor. Adsorption of CP 1 obeyed Langmuir adsorption isotherm. Effect of temperature on the corrosion process was studied and activation parameters were calculated and discussed. The results obtained from the two different electrochemical techniques are in good agreement.