Synthesis and characterization of Mn(II) complexes of 4-phenyl(phenyl-acetyl)-3-thiosemicarbazide, 4-amino-5-phenyl-1,2,4-triazole-3-thiolate, and their application towards electrochemical oxygen reduction reaction

Two new complexes, [Mn(ppt)2(o-phen)] (1) and [Mn(aptt)(Cl)(o-phen)2]·2Haptt·H2O (2) with 4-phenyl (phenyl-acetyl)-3-thiosemicarbazide (Hppt) and 4-amino-5-phenyl-1,2,4-triazole-3-thiolate (Haptt) have been synthesized containing o-phenanthroline (o-phen) as a coligand. Both complexes are paramagnetic and have a distorted octahedral geometry. In complex 2, two molecules of Haptt and one water molecule are also cocrystalized outside the coordination sphere. Complexes 1 and 2 are fluorescent and upon their excitation at 38 167 cm−1, exhibit emissions at 27 173 and 32 894 cm−1, respectively. TGA of complexes 1 and 2 indicate that the metal is converted into metal oxide at very high temperature. To explore the possible electrochemical applications of the complexes 1 and 2, they are immobilized on glassy carbon electrode using Nafion®. Both complexes demonstrate excellent electrocatalytic activity towards electrochemical oxygen reduction. [Display omitted] Two new complexes, [Mn(ppt)2(o-phen)] (1) and [Mn(aptt)(Cl)(o-phen)2]·2Haptt·H2O (2) with 4-phenyl (phenyl-acetyl)-3-thiosemicarbazide (Hppt) and 4-amino-5-phenyl-1,2,4-triazole-3-thiolate (Haptt) have been synthesized containing o-phenanthroline (o-phen) as a coligand. These complexes have been characterized by elemental analyses, IR and UV–Vis spectroscopic techniques, thermogravimetric analysis (TGA), magnetic susceptibility and single crystal X-ray diffraction data. The complexes are paramagnetic and have a distorted octahedral geometry. In complex 2, two molecules of Haptt and one water molecule are cocrystalized outside the coordination sphere. Complexes 1 and 2 are fluorescent and upon their excitation at 38 167 cm−1, exhibit emissions at 27 173 and 32 894 cm−1, respectively. TGA of complexes 1 and 2 indicate that the metal is converted into metal oxide at very high temperature. In the solid state, the crystal structure of both complexes are stabilized by various inter and intramolecular interactions. To explore the possible electrochemical applications of the complexes 1 and 2, they are immobilized on glassy carbon electrode using Nafion®. Cyclic voltammetry technique is used to characterize the metal complex immobilized electrodes in basic medium. Both complexes demonstrate excellent electrocatalytic activity towards electrochemical oxygen reduction. Since the electrocatalytic materials for oxygen reduction can dramatically increase the efficiency of the fuel cells and metal-air batteries, these meta