Eight different nickel porphycenesbearing substituents on the pyrrole β and/or ethylenic carbonpositions of the macrocycle were investigated as to their redoxproperties in benzonitrile containing 0.1 M tetrabutylammoniumperchlorate. Half-wave potentials were utilized to evaluate theeffect of substituents and extended conjugation on theelectrochemically measured HOMO−LUMO energy gap which is given byΔE1/2 =E1/2(first oxidation) −E1/2(first reduction) and ranges between1.33 and 2.01 V.
