Porphyrazine structures

Fig. 3 - Some typical porphyrinic molecules a) Ni star-porphyrazine, with four fused thiolene groups (4PZ), b) basic porphyrazine structure with peripherally fused-benzo rings (PC) and c) dithiolene groups (PZ).

Figure 1. Structural distinctions between porphyrins and porphyrazines.

Electronic Structure. The electronic spectra of these S-methyl porphyrazines are discussed in Section II. 

Structural Characterization. Solitaire porphyrazines (67b and 67h) have been crystallographically characterized (4). As Table XVI indicates, the Cp-Cp-S angles and S-S distances for 67b and 67h are significantly smaller and shorter than those reported for the uncoordinated. V-methyl pz 46. These smaller bond angles and shorter bond distances are attributable to the... 

Structural Characterization. The crystal structure of 83 (Fig. 15) surprisingly revealed eight Ag+ ions coordinated to the periphery of the porphyrazine—four bound in an endocyclic fashion by the crown moieties, consistent with the optical data, and four coordinated to the meso pockets in a (S-N-S) tridentate coordination geometry. The lack of evidence for meso coordination in solution suggests a preference for the ligation of Ag+ by the crown moieties (25). 

Thiadiazole and selenodiazole rings are isoelectronic with benzene and form a fully conjugated, essentially planar structure when fused to porphyrazines at the p-pyrrolic position (168). Compared to pc, the incorporation of sulfur and selenium in addition to nitrogen atoms to the peripheral heterocyclic rings affects the electronic charge density and influences the interactions between adjacent molecular stacks. 

The peripheral selenodiazole rings of porphyrazine (169) can be opened upon treatment with H2S with the proposed formation of the octaaminoporphyrazine (184), which was not isolated and instead converted into the tetrakis(pyrazino)porphyrazine (185) (Scheme 34) (171). Other heterocycles have been fused on the periphery of porphyrazines, such as l,3-dithiol-2-thione in order to extend the aromatic core (172). Macrocyclization of 4,5-dicyano-l,3-dithiole-2-thione (186) under Linstead conditions in the presence of magnesium butoxide produced the symmetrically substituted tetrakis(l,3-dithiol-2-thiono)porphyrazine (187) (Scheme 35). Due to the low solubility of porphyrazine 181, a consequence of the planar aromatic molecular structure, a full characterization of this compound could not be accomplished. 

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