90 HI. PORPHYRIN CHEMISTRY 



Monoazaporphyrins were synthesized by heating a, oi'-dibromopyrrome- 

 thenes with sodium hydroxide (SH), as a by-product of the synthesis of 

 diazaporphyrins on heating a, a'-dibromopyrromethenes with ammonia 

 {84'j), and from pyrromethenes bearing a bromomethyl group in a- and a 

 urethane group ina'-position (688). None of these syntheses has an unequivo- 

 cal reaction mechanism. 



It is therefore important that the structure of monoazaporphyrin 

 has been estabhshed in an entirely different and simple way by 

 Lemberg {1687). If verdohematin compounds in which one of the 

 methene groups of the porphyrin ring has been removed by oxida- 

 tion (c/. Chapter X) is treated with ammonia, monoazahematin 

 compounds are formed. The reaction can be formulated as: 



C r C C C C 



V — ^ VI ^ ^N^ 

 H OH 



By treatment of monoazamesohemin with hydrazine hydrate in 

 acetic acid, monoazamesoporphyrin is obtained, the absorption 

 spectrum of which agrees well with that of monoazaetioporphyrin of 

 Fischer and Friedrich (814,2639). The absorption bands of mono- 

 azamesoporphyrin in ether-acetic acid are: I, 614; la, 588; II, 562; 

 III, 534; IV, 502 m/i. 



The influence of the side chains on the position of the absorption bands 

 of azaporphyrins and their compounds is exactly the same as with the por- 

 phyrins. The bands of the proto compounds with vinyl groups lie about 

 10 mju nearer to infrared. In their neutral absorption spectrum and their 

 red fluorescence, the monoazaporphyrins closely resemble porphyrins (cf. 

 also their iron complex salts. Chapter V), and they also show the strong band 

 in the ultraviolet (2189). The absorption spectrum of monoazamesopor- 



N N 



Fig. 2i. Diazaporphyrins. Fig. 23. Tetraazaporphyrins. 



phyrin solutions in hydrochloric acid shows positions of the absorption bands 

 similar to those of mesoporphyrin (.595,551 mju), but the first band is stronger 

 than the second. The fluorescence spectra of the solutions in hydrochloric 

 acid also differ (26^3). 



