Voltammetric Characterization of the Electrochemical Redox Behaviour of N-Thiocarbamoyl-benzamidines and 1,2,4-Thiadiazolium Salts

摘要

The Electrochemical redos behaviour of N-(diethylamino-thiocarbamoyl)-benzamidines Et_2N-C(S)-N=C-(NHR)-Ph (1:R=H; 2:R=n-C_3H_7; 3:R=Ph) and 2,3-diphenyl-5-diethylamino-1,2,4-thiadiazolium iodide (4) as well as of its perchlorate (5) was studied by cyclic voltammetry in ethanolic solution at a glassy carbon electrode between -1.2V and +1.5V vs. Ag/AgCl. The mechanisms for the irreversible anodic oxidation of the benzamidines 1-3 and the formed products (1,2,4-thiadiazolium cations or 1,2,4-thiadiazole) are influenced directly by the substituents bound to the terminal benzamidine nitrogen atom. In the cathodic potential range, an irreversible reductive cleavage of the benzamidines 1-3 occurs which also depends on the N-Bound substitutents. The products of this reduction, which are identified indirectly electrochemically by comparing voltammogramms, can be adsorbed on the electrode surface and reoxidized in the following anodic scan. The 1,2,4-thiadiazolium cation of 4 and 5 is redox inert in the investigated anodic potential range. The obtained anodic peaks in the case of 4 result from redox reactions of the iodide counter ions only. However, the 1,2,4-thiadiazolium cation is also subject of a reductive cleavage in a similar way to the mechanism which is proposed for the N-thiocarbamoyl-benzamidines 1-3. The discussed electrochemical redox mechanisms of the characterized compounds 1-5 are compatible with known results of synthesis.