Synthesis, crystal structure, and electronic absorption of chlorophyll derivatives possessing a β-diketonate moiety at the C3 position

A chlorophyll-a derivative possessing a trifluoroacetylacetonate moiety at the C3 position was prepared by Claisen condensation of the 3-acetyl group with ethyl trifluoroacetate in the presence of sodium methoxide. The Claisen condensation was successfully applied for the reaction of 3-acetyl-chlorin with ethyl pentafluoropropionate as well as that of 3-acetyl-bacteriochlorin with ethyl trifluoroacetate. The resulting Claisen condensation products took exclusively diketonate conformers in a CDCl3 solution and the single crystal, and gave red-shifted and broadened Qx/Qy absorption bands in the visible to near-infrared region, compared with the corresponding 3-acetyl-(bacterio)chlorins.