178 



LIGHT AND LIFE 



Fluo 



rescence 



Chemiluminescence 



to 



•ki 

 Q 



CL 



Wavelength (a) 



Fig. 3. Comparison of fluorescence and chemiluminescence spectra of zinc tetra- 

 phenylporphine at 148°C. (The indicated wavelengths are neon calibration lines). 



luminescence in hot peroxide solutions (Kalberman, 7) . If anything, 

 addition of TPP slightly inhibits peroxide decomposition. The pres- 

 ence of the complexed metal is therefore a strict requirement, in 

 agreement with the findings of Cook in hydrogen peroxide systems 

 (2) . It is difficult to compare the effectiveness of the various TPP 

 metal complexes which were tested, because of the widely different 

 stabilities of the metallo-porphyrins. However, the order is approxi- 

 mately Cu > Pb > Zn > Sn. Of these, the copper salt is by far the 

 strongest catalyst, as shown by Kalberman (7) . 



Discussion 



The first question to be decided is whether we are observing a true 

 catalysis or merely a stoichiometric reaction between peroxide and 

 porphyrin. There is certainly no doubt that a certain fraction of the 

 total peroxide decomposed is used to break down the dye. On the 

 basis of other studies (5, 6) establishing formation of pthalimide 

 and ammonia from metallo-phthalocyanines in the peroxide reaction, 

 we might expect that succinimide and jiossibly benzoic acids would 

 result from ZnTPP breakdown. It is not likely, however, that each 

 ZNTPP molecide would require as many as thirty molecules of 

 peroxide, wliich is the observed ratio. If ^\•e confine ourselves to the 



