Molecular orbital study of the porphyrins

Abstract

An LCAO molecular orbital calculation has been carried out for models of porphin and its hydrogenated derivatives, chlorin, a and β tetrahydroporphin, and hexahydroporphin. Application of the results to the spectra of these compounds has provided a consistent interpretation in terms of relative energies of the two highest filled molecular Orbitals. Comparison is made largely with the observed spectra of zinc tetraphenylporphyrins. The calculation confirms the proposed structural assignments for α and β tetrahydroporphins. The use of Tschebycheff polynomials in solving secular equations is described.