Abstract:
The role of aromatic subunits is crucial to the structural and electronic properties of isophlorin and its expanded derivatives. Herein we describe the effect of benzene ring substitution in a 32π expanded isophlorin core, which is at the crossroads of hexaphyrin and octaphyrin. Synthesis, structural characterization and electronic properties of a non-planar 32π core-modified expanded isophlorin resembles that of a hexaphyrin like macrocycle. Dibenzi hexaphyrin is known to retain a planar structure; however, the dibenzi expanded isophlorin reported here loses its planarity and is found to adopt a unique V-shaped structure. The non-antiaromatic nature observed from spectroscopic analysis is ably supported by computational studies. Electronic absorption studies and mass spectrometry support a two-electron ring oxidation as expected of antiaromatic macrocycles.