Design and synthesis of a sterically locked, highly distorted phthalocyanine and observation of all possible stereoisomers

Disruption of the planarity of porphyrinoid cores significantly impacts both spectroscopic and solubility properties and is a useful tool in molecular design. Here, we present the synthesis of a highly distorted phthalocyanine from a rigid, laterally extended phthalonitrile in which the extension is directed toward the core. This arrangement challenges macrocycle formation and aromatisation, such that forcing conditions and zinc templating are required. The phthalocyanine formed is a mixture of 4 isomers (2 of which are chiral, so there are 6 stereoisomers in total) and each of them is sterically locked. They can be distinguished by NMR spectroscopy, and careful separation and crystallisation allow the two most abundant isomers to be isolated. Crystal structures and the absorption spectra of these two isomers are reported.