Abstract

The redox chem. of the manganese(II) and manganese(III) complexes with 1-​isoquinolinecarboxylate (1-​IQC) in DMSO was studied. Cyclic voltammetry, polarog., controlled-​potential electrolysis, UV-​visible spectroscopy and magnetic susceptibility measurements were performed on the solns. In the presence of the anion 1-​isoquinolinecarboxylate the manganese(II) ion forms an MnII(1-​IQC)​2 complex, whose conditional formation const. was evaluated polarog. and turns out to be 5 × 107 M-​2 at 25°. The polarograms of the soln. of this complex show a cathodic wave with E1​/2 = -​1.60 V vs. SCE, corresponding to the redn. of the metal ion with its subsequent destruction. However, the voltammograms on a platinum electrode show the redn. of the bound ligand at -​1.66 V vs. SCE, probably to a bound radical species, and 2 oxidn. processes at -​1.37 and -​1.49 V vs. SCE. The manganese(II) complex does not decomp. after this redn., but the species produced was not obtained quant. as the redn. potential was too close to the solvent discharge. The manganese(II) complex is oxidized to the MnIII(1-​IQC)​3 mononuclear complex, whose conditional formation const. was evaluated polarog. and turns out to be 4 × 1014 M-​3 at 25°.