In vitro complexes of copper and zinc with chlorophyll

Complexes of copper and zinc with chlorophyll, the major photosynthesis pigment, were studied by Vis, FTIR and fluorescence spectroscopy. Two types of complexes were recognized. While copper replaces the central magnesium atom of chlorophyll to form a "central" Cu-Chl complex, this was not proposed in the case of zinc. Instead, the zinc-mediated formation of a 6-membered chelate cycle fused at the periphery of the chlorophyll structure is proposed. The latter event could be ascribed to allomerization reactions of chlorophyll.