Thiadiazoles and selenodiazoles

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. 

Electronic Spectra of Thiadiazole and Selenodiazole Porphyrazine Complexes 2... 

The Hurd-Mori cyclization and Lalezari cyclization of a-methylene ketones are by far the most widely used routes to 1,2,3-thiadiazole and 1,2,3-selenodiazole, respectively.This approach has been applied in the synthesis of a variety of 1,2,3-thiadiazoles 129 (13JHC630) andl31 (13OT4038) from the corresponding hydrazones. Thiadiazoles 132, derived from 131, can be effectively converted to benzothiophene derivatives (see Section 5.5.4.2). 

The optical spectra of the selenodiazole appended porphyrazines 169, 171, and 172 show maxima of Q bands that are closer to those obtained from phthalocyanines, whereas they differ by 30-40 nm from those of thiadiazole derivatives (174). No splitting of the Q bands was observed for the... 

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