Salen-pyrrole ligands

Mitchell and Valero (1982, 1983) studied VO-phthalocyanine (VO-PC) and a Schiff base complex, VO-salen, as model vanadium compounds. The VO-PC provides a metal coordination environment comprised of four nitrogens, similar to the porphyrin. The benzo rings at the /3-pyrrolic positions contribute to enhanced aromaticity in the metal ligand. 

Transition-metal porphyrin complexes are found in such important proteins as hemoglobin, chlorophyll, and the cytochromes. Because of their biological significance, porphyrins and their simpler analogs have been extensively studied in the laboratory. Porphines and their close cousins the salens (salicylaldehyde eth-ylenediamine) are tetradentate, six-electron ligands, with two one-electron donors and two two-electron donors. Porphines are macrocycles made up of four pyrroles... 

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