Fluorescence Efficiencies of Organic Compounds

The relative fluorescence efficiencies of a large number of organic compounds of different structures were measured in solution under high-energy and ultraviolet excitations. P/R values of the more efficient solutes under high-energy excitation are given. Where possible at room temperature the fluorescence under high energy was also determined for the compound in solid form. A considerable parallelism is found between the relative fluorescence efficiencies in solution under both modes of excitation. Oxygen effects were measured and found to be greater on the solvent than on the solute, but do not greatly influence the relative efficiencies. Changes in fluorescence produced by substituents which do not considerably alter the absorption spectrum are discussed.