| Abstract: | Abstract Beelen and coworkers in the Netherlands recently reported that visible light enhanced the rate of selective oxidation of mercaptoethanol by dioxygen, catalyzed by cobalt (II) tetrasulfonated phthalocyanine (CoTSPC). The Dutch workers speculated that visible light promoted disaggregation of CoTSPC, producing more of the catalytically active monomer. If Beelen and associates are correct, then it is possible that the values for the dimerization constants of CoTSPC are in error. since the values were measured spectrophotometrically in the region of the spectrum where Beelen contends visible light promtes disaggregation. To test whether the dimerization constants are altered by the spectrophotometer, the absorbance of a CoTSPC solution was measured with a diode array UV-VIS spectrophotometer. By comparing the spectrum of CoTSPC in the UV region with the tungsten lamp active and then inactive, one can see whether the visible light affects aggregation. It turned out that no change was observed in the spectrum of CoTSPC when the tungsten lamp was turned off, so the dimerization constants measured in the visible region of the spectrum are not affected by the spectrophotometer. |
