Significant shifts in the Cu 2p 3/2 and N 1s spectra were observed with respect to Cu(DAT). X-ray photoelectron spectroscopy was utilized to analyze the composition of the deposition. The activity increased significantly in the course of time. Rotating ring disk electrode experiments showed that this deposition is an active ORR catalyst which reduces O 2 all the way to water at pH 5. Electrochemical quartz crystal microbalance experiments displayed a large decrease in frequency below 0.5 V versus the reversible hydrogen electrode (RHE) in a Cu(DAT) solution implying the formation of deposition. Monitoring the typical 380 nm peak with UV-Vis spectroscopy revealed that the Cu 2(μ-DAT) 2 core is extremely sensitive to changes in pH, copper to ligand ratios and the presence of anions. The electron paramagnetic resonance (EPR) spectrum of Cu(DAT) showed a broad axial signal with a g factor of 2.16 as well as a low intensity M s = ☒ absorption characteristic of the Cu 2(μ-DAT) 2 moiety. The water soluble dinuclear copper complex ( Cu(DAT)) was obtained by mixing a 1 : 1 ratio of Cu(OTf) 2 and DAT in water.
In this study, the active species for the ORR was investigated. Dinuclear Cu II complexes bearing two 3,5-diamino-1,2,4-triazole (DAT) ligands have gained considerable attention as a potential model system for laccase due to their low overpotential for the oxygen reduction reaction (ORR).