[2-Methylazeteochlorinato]Ni(II): a pyrrole ring-contracted chlorin analogue

The formal replacement of one of the pyrrole rings in [meso-tetraphenylporphyrinato]Ni(II) (5Ni) by an azete moiety is reported. Thus, reaction of known chlorophin monoaldehyde 7Ni (made in three steps from 5Ni) with methyl-Grignard, followed by an acid-catalyzed ring-closure reaction, generates the title compound [meso-tetraphenyl-2-methylazeteochlorinato]Ni(II) (10Ni) in a rational and scalable process in good yields. The UV–vis spectroscopic properties of this chromophore are, as expected for this chlorin analogue, red-shifted when compared to the corresponding [porphyrinato]Ni(II) (5Ni) complex. A much improved synthesis of the starting material 7Ni by Vilsmeier–Haack formylation of [meso-tetraphenylchlorophinato]Ni(II) (8Ni) is also reported.