Photophysical properties of zinc and magnesium tris(pyrochlorophyllide a ) 1,1,1-tris(hydroxymethyl)ethane triesters

Abstract

The Zn and Mg tris(pyrochloro-phyllide a) 1,1,1-tris(hydroxymethyl)ethane triesters have properties that are very similar to those exhibited by pairs of pyrochlorophyll a or chlorophyll a linked by ethylene glycol through their propionic acid side chains. In the open configuration, the fluorescence lifetimes and emission spectra of the triesters resemble those of chlorophyll a monomers. However, the triesters have a mechanism for energy dissipation not present in monomeric chlorophyll a, which prevents the build-up of significant concentrations of molecules in S1 states. Optical pumping of these compounds in their folded configuration results in the formation of high concentrations of molecules in S1 states and in laser light emission, which originates from the 2-folded macrocycles. Efficient energy transfer may occur from the open to the folded configurations.