Mutual atomic effect in porphyrin molecules and its manifestation in their structure and electronic absorption spectra

The state of the art and trends in development of the concepts of the mutual atomic effect in molecules of porphyrins and organic and complex compounds are reported. The electronic effects of coordination in metalloporphyrin molecule and those of aza- and benzosubstitution in porphyrins-ligands are considered in the context of the chromophore-auxochrome theory. The particular role of the proton as the strongest auxochrome is noted.