DISCUSSION 197 



you ;irc suo;<;e.stinj> vvhidi might change your rate constant in the first few 

 seconds. Why doesn't it continue to change yoin^ constant? 



Dr. Lin.sc:iiii/.: I lie only way that 1 can make sense out ol tlial is to 

 assume that there is a steady state concentration ol the inhibitor which is 

 maintained more or less constant during the course of the reaction. The 

 best source of this would probably be some intermediate breakdown product 

 of the dye, which is extensively decomposed. If you start, for example, with 

 phthalocyaninc, you obtain phthalimide as the end product of the dye 

 breakdown. The final absorption spectrum of our reacted solutions shows no 

 traces of any long wavelength absorption components. You really shatter 

 the dye. The breakdown of the dye itself apparently needs metal. If you run 

 this reaction in the presence of uncomplexed porphyrin, then the dye rides 

 right through and there is apparently little attack on the dye. That is rather 

 surprising because presumably the uncatalyzed normal breakdown of peroxide 

 must go through some chain prcicess inxolving hydroxyl. And yet the 

 porphyrin structure seems to come through hydroxyl radicals unchanged. 



Dr. Platt: How great a range of metals have you tried? 



Dr. Linschitz: Not too great: zinc, magnesium, lead, tin and copper. I 

 know that this is rather a bizarre choice of metals. It was made for 

 spectroscopic as well as chemical reasons. 



Dr. Platt: ^Vould the disodium complex work as well? 



Dr. Calvin: I do not think that this compound would last through the 

 peroxide treatment. Would copper really work as well as the other metals? 

 The other metals are all diamagnetic. 



Dr. Linschitz: Well, I have a feeling that the magnetism per se does not 

 play any important role in the catalysis. Copper is extremely active. 



Dr. Calvin: But can you get chemiluminescence? 



Dr. Linschitz: You do not get the luminescence, but then the copper 

 complex does not fluoresce. 



Dr. Calvin: But that is just the point. 



Dr. Linschitz: Yes, that's the point. It may very possibly go through some 

 excited state, but you never see it, because the copper porphyrin immediately 

 falls over quite likely to the triplet, and then very cjuickly to the ground 

 state. It is a very active catalyst for the peroxide breakdown, much more 

 active than the other metals. 



Dr. Weber: I wanted to make some remarks on the general energetics 

 of luminescent reactions. It has been said many times that these reactions 

 are strongly exothermic. What has not been used to my knowledge is the 

 balance of the bonds broken and formed during the reactions to calculate 

 AH which is approximately equal to SF. This should give us some idea of 

 how much energy we should get in the reaction. For example, in the peroxi- 

 dation of an aldehyde there is one carbon-hydrogen bond broken which 

 rec|uires 85 kilocalories and one oxygen-oxygen bond broken which recjuires 

 40 kilocalories. One carbon-oxygen bond is formed releasing 75 kilocalories, 

 and one oxygen-hydrogen bond formed releasing 110 kilocalories. Thus, the 



