OXYPORPHYRINS 91 



Diaza- and teiraazaporphiirins have also been synthesized USJt,6SS,S09, 

 821,1921). The absorption and fluorescence spectra of these compounds in 

 neutral solvents again resemble those of porphyrins. They show the absorp- 

 tion band in the ultraviolet, but the first absorption band in the red is much 

 stronger and the fourth band in the blue-green weaker (2189,2638,2639,26^, 

 2613). The absorption spectra of the green hydrochlorides are quite differ- 

 ent from those of porphyrins, however, suggestuig salt formation on the 

 nitrogen atoms connecting tlie pyrrole rings. The salts do not fluoresce. 

 The absorption spectrum of phthalocyanins, while difi'ering considerably 

 from that of tetraazaporphyrins, still shows some similarity in type (2639). 



Azapyrromethenes have been synthesized by Rogers (2330). 



8.2. Oxyporphyrins 



Green oxidation products containing two more oxygen atoms than por- 

 phyrins were obtained by Fischer {861, pp. 269-274; 816,857,887) from 

 etioporphyrin and mesoporphyrin by treatment with hydrogen peroxide in 

 concentrated sulfuric acid. At first formulas with hydroxyl groups on the 

 methene groups (I, Fig. 24) were assumed for these compounds, later addi- 

 tion of hydrogen peroxide on two adjacent positions of one pyrrole nucleus 

 (II, Fig. 24) was preferred by Fischer {861). By treatment of the copper 

 complex of dioxymesoporphyrin with concentrated sulfuric acid a monoxy- 

 mesoporphyrin was obtained, to which the structure III (Fig. 24) maj' be 

 ascribed. The absorption spectra of dioxy- and mono.xymesoporphyrin do not 

 differ (Stern and Dezelic, 2633). Both porphyrins have high HCl numbers, 

 e.g., monoxymesoporphyrin 14.5. 



A different tj^e of oxyporphyrin was obtained by Lemberg and co-workers 

 (1698) by oxidation of pyridine hemochrome with small amounts of hydro- 

 gen peroxide in the presence of ascorbic acid, and by splitting of the red- 

 brown oxyporphyrin hemochrome thus obtained with hydrochloric acid 



Fig. 24. Oxymesoporphyrins of Fischer. 



under nitrogen. By further oxidation the hemochrome was easily tran.s- 

 formed into verdohemoclirome with removal of one of the methene groups 

 between pyrrole rings (rf. Chapters V and X). This suggested that liie first 



