Synthesis of new macrocyclic rhodium(III) compounds and their utility as catalysts for the oxidation of ascorbic acid

Ten new macrocyclic Schiff base Rh(III) compounds were synthesized by treating the corresponding macrocycles with rhodium chloride in 1:1 ratio. The resulting compounds were characterized by elemental, IR, ¹H NMR, ¹³C NMR, mass, electronic spectral analysis, and their structures have been proposed. These compounds were utilized as catalysts in the development of an efficient and environmentally friendly catalytic method for the oxidation of ascorbic acid (AA) to dehydroascorbic acid (DHAA). DHAA was determined spectrophotometrically by treating with orthophenylenediamine (OPDA) and the yields were found to be in the range 72–84%. The catalytic oxidation and spectrophotometric determination methods were found to be faster and more accurate than those reported previously.