Planarity of metal chlorins in n-octane solution

The geometry of porphyrins has been and continues to be a subject of vigorous research. In this work we investigated the planarity of a series of divalent metal chlorins in n-octane solutions: magnesium, zinc, copper, nickel, cobalt, manganese, tin, cadmium, strontium, lead and platinum. Room temperature electronic absorption spectra of these complexes are reported. We plotted the energy of each B band against its respective Qy origin band. Based on these results it was concluded that in these metal chlorins the configuration interaction between Qy and B states is essentially constant; the exception is the magnesium complex which deviates from the pattern produced by the other metal chlorins. This suggests that the magnesium ion is out of the plane of the chlorin skeleton; thus, it has C(S) symmetry while the other metal chlorins in this group retained C2v symmetry.