Spectroscopic Studies of Methimazole Reactivity toward the Aquapentacyanoferrate (II) Ion in Aqueous Solutions

Abstract

Methimazole (2-mercapto-1-methylimidazole, MMI) and its pentacyanoferrate (II) complex have been characterized by means of UV/Vis, Raman, and NMR spectroscopy. The reaction of MMI with aquapentacyanoferrate (II), [Fe(CN)5(H2O)]3−, in buffered aqueous solutions yielded the [Fe(CN)5(MMI)]3−complex. It was found that only thione tautomer of MMI coordinates to the iron (II). The exceptionally stabile and inert complex was produced.

Metal(II) Ion Complexes with 5‐(Pyrazin‐2‐yl)‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thione; Synthesis, Structural Characterization, Acid‐base, and Complexing Properties in Solution

“…However, the analysis of all titrations show that the refined number of accessible protons originating from the ligand was around 10 % lower than the number resulting from the total concentration value. Thus, it may be presumed that coordination occurs due to a dissociable proton of one of the tautomeric forms, most likely the thione form usually predominating in non‐basic medium , . The dissociation constant of the ligand was confirmed with high accuracy, p K a = 5.76 ± 0.01.…”