112 



RADIATION BIOLOGY 



derivatives, and its 6-acrylic acid analogue (compounds 14-26 in Fig. 

 2-22). Second-order effects with these strong moments might account 

 for part of the discrepancy. But it is a firm prediction of the theory 

 that the 7-alkyl derivative (chloroporphyrin-e4 and -ee, compound 17), 

 with a positive moment, and the 7-carboxyl derivative (compound 19), 

 with a negative moment, should affect the rhodoporphyrin intensity 

 oppositely. This is exactly contradicted by the fact that in band III 

 both derivatives have intensities well below rhodoporphyrin XV itself. 



With isocyclic rings (predictions tentative) 



9 

 10 

 11 

 12 

 13 

 14 

 15 



Pyropheojihorbide o and pheophytin a 



Pheophorbide a 



Dihydro-(8) 



Methyl chlorophyllide a 



Pyropheophorbide 6 



Pheophorbide 6 



Dihydro-(12) 



2-Cyclopropyl-(12) 



2-Cyclopropyl-3-formyl-(12)-oxime 



28, 

 52, 

 29, 

 39, 

 76, 

 40, 

 37, 

 38, 

 77, 



11; 



IV 



II 



III 



V 



III 



III 



III 



V 



V 



~#- 



*- 



— #- 



— f 



Mg 



C 



c 

 c 

 c 

 c 

 c 

 c 

 c 



" Substituents designated as in Table 2-3, "Code" column. 



f" P, porphyrin polarization; C, chlorin polarization; see Fig. 2-20. 



* Isocyclic ring — CH2 — CO — between y and 6 positions. 



f Isocyclic ring — CHCCOOCHs) — CO — between y and 6 positions. 



In view of the many other qualitative successes of the theory, as shown 

 in Fig. 2-22, this direct qualitative contradiction suggests, at least to the 

 author, that one of these compounds and possibly some of the other sub- 

 stituted rhodoporphyrins were either impure or misidentified. (This is 

 known to have happened with a few of Stern and Wenderlein's compounds 

 and is not surprising, since their measurements were made at a time when 

 syntheses and structural determinations were still in a formative stage.) 



Isocyclic Rings and Metal Complexes. The data are insufficient for 

 determining uniquely the moments and directions for isocyclic rings con- 

 necting positions 6 and 7, such as occur in some of the most interesting 

 compounds. We can still get a prediction of the band I intensity in 

 pheophorbides and pheophytins, which have the bridge — CH2— CO— 

 or — CH(C00CH3)— CO— between positions 7 and 6. Stern and Wen- 



