Bis(dimethylamino)porphyrazines: synthetic, structural, and spectroscopic investigations

The synthesis and isolation of unsymmetrical porphyrazines bearing two, four, and six bis-(dimethylamino) functionalities has been achieved via the base-catalyzed cross-condensation of 1,2-dicyanobenzene 8 and bis(dimethylamino)maleonitrile 7. In addition, the benzo-fused hexaaminoporphyrazine dimer 10 was prepared from condensation of dinitrile 7 (in excess) with benzenebis(1,3-diiminopyrroline) 9. Electrochemical studies reveal that all porphyrazines may be readily oxidized. The X-ray structures of porphyrazines 2b and 5a and the cis isomer 3a are presented. The latter is the first structure of a porphyrazine having a cis-type substitution pattern. The extended pi-conjugation in dimer 10 causes a approximately 100 nm red-shifted Q-band in the electronic absorption spectrum.