Die Reaktivitäten des Porphins, Chlorins, Bacteriochlorins und Phlorins. Ladungsdichten, Freie Valenzen und Außenelektronendichten / The Reactivities of Porphin, Chlorin, Bacteriochlorin, and Phlorin. Electron Densities, Free Valences and Frontier Orbital Densities

Abstract

The π-electron densities, bond orders, free valences, and reactivity indices according to Fukui's “frontier orbital”-model were calculated for all reactive centers of porphin, chlorin, bacteriochlorin and phlorin by means of Self Consistent Field (SCF) calculations using the approxima tiaons of Pariser, Parr, and Pople. The results were compared with known experimental facts. The relative reactivities of different reactivity centers (e. g. methine-bridges and β-pyrrolic carbon atoms) are well predicted by calculated π-electron densities, whereas the characteristics of similar reactivity centers (e. g. the different methine-bridges in chlorin) are better reflected in the reactivity indices of the “frontier orbital’ model. Reasons for the partial inadequacies of the models used are shortly discussed.