Abstract
Two new iron(III) compounds, (Hamp)[Fe(pydc)2] · 2H2O (1) and (Hacr)[Fe(pydc)2] · 2H2O (2) (pydc2− = pyridine-2,6-dicarboxylic acid, amp = 2-aminopyrimidine, acr = acridine), have been hydrothermally synthesized. Both compounds were characterized by spectroscopic methods (IR, UV/Vis), and their molecular and crystal structures were determined by X-ray crystal structure analysis and their thermal stability by thermogravimetric analysis/differential thermal analysis (TGA/DTA) methods. Compound 1 consists of Hamp+ cation and [Fe(pydc)2]− anion and 2 consists of Hacr+ cation and [Fe(pydc)2]− anion. Crystallographic characterization revealed an octahedron as a coordination polyhedron for the complex anion in 1 and 2 and the same O,N,O′-chelated coordination mode of pyridine-2,6-dicarboxylate. The crystal structures of 1 and 2 are stabilized by a complicated network of hydrogen bonds between the crystallization water molecules, counter ion, and carboxylates of pydc2−. Thermogravimetric (TG) analyses of the two compounds were carried out to examine their thermal stabilities. Cyclic voltammetric response of bare glassy carbon electrode surface in 0.10 mol L−1 phosphate buffer containing 1 and 2 at different pH values indicated that they have the same voltammograms at all pH values and the electrochemical behavior of 1 and 2 has not been affected by different ion pairs. The formal potential of the solutions of 1 and 2 at the glassy carbon electrode surface was also pH-dependent with a slope of −57.0 mV/pH unit at 25°C. This shows that the number of electrons and protons involved in the electrode process is equal.
Acknowledgments
This research was supported by the Ministry of Science, Education and Sports of the Republic of Croatia (Grant no. 119-1193079-1332), and Islamic Azad University, Yazd Branch.