Molecular orbitals and electronic spectra of benzo-fused and related porphyrin analogues

Molecular orbital (MO) calculations of more than 60 porphyrinic π conjugated structures have been performed within the framework of the Pariser–Parr–Pople approximation. The results of a series of compounds are introduced and summarized in order to show how they vary depending on the systematic change in molecular structure. These are shown schematically or itemized. Our results are compared with the spectra of the corresponding known compounds and with the MO results reported by previous workers, if available. In addition, the results have continually been compared, where possible, with those of tetraazaporphyrin or phthalocyanine systems. In naphthalene- or anthracene-fused compounds, these molecule-centered orbitals often appear, and these are indicated using either triangles or circles in figures if they appear between HOMO – 3 and LUMO + 3 orbitals.