Using a bio-inspired copper complex to investigate reactive mass transfer around an oxygen bubble rising freely in a thin-gap cell.

For the first time the formation and decay of the thermally very sensitive bis(μ-oxo)dicopper species was monitored at ambient temperature in a continuous flow setup and the rate constant of the decay was measured.

Combining the new aromatic bis(guanidine) ligand bis(tetramethylguanidino)toluene (TMG2tol) and different copper salts led to four new complexes. The molecular structures were analysed by X‐ray diffraction. Three of the complexes are active in biomimetic activation of oxygen. It is the first time a bis‐µ‐oxido species of an aromatic guanidine copper complex is analysed by Raman and UV/Vis spectroscopy. The formation and decay of the bis(µ‐oxido)dicopper species were investigated at low temperatures up to 273 K by UV/Vis spectroscopy with a stopped‐flow setup. The results showed that the Cu2O2 intermediate of an aromatic guanidine–copper complex decays much faster than most known bis(guanidine) complexes. Moreover, natural bond orbital (NBO) analyses revealed that the aromatic guanidine is the stronger donor compared to the aliphatic one.