Although the high fluorescent intensity of Bodipy dyes makes them desirable for use in biochemical assays, their excitation and emission spectra are so close that researchers cannot discriminate between them. Chemists have modified these dyes to contain two chromophores, so that the rapid intramolecular transfer of the chromophores artificially creates a larger Stokes shift. One group of chemists recently synthesized two-chromophore Bodipy dyes that transfer intramolecular energy more efficiently. Researchers at the University of Newcastle in the UK and at Centre National de la Recherche Scientifique in Strasbourg, France, detail the production and properties of the dyes in the Aug. 10 ASAP edition of the Journal of the American Chemical Society. As others have done, they added an aromatic polycyclic compound that transfers energy to the Bodipy dye. However, they replaced the fluorine atoms of the dye with the compounds, rather than attaching them to the Bodipy framework with an ethylnylene linker. Whereas previous synthesis necessitated the use of symmetrical polycyclic compounds, this method allowed the scientists to attach two different compounds, enabling them to create unique spectral properties. The scientists created three dyes with similar properties. The polycyclic compound did not affect the spectral profile of the Bodipy dye, unlike the past method of synthesis. The dyes absorbed a broad range of wavelengths, from 250 to 530 nm, and they had a quantum yield of 0.9 ±0.05 and a fluorescence lifetime of 6.5 ±0.1 ns. The fluorescence quantum yield did not change greatly with polarity or temperature. Using an excitation wavelength of 480 nm, the dyes emitted light at 550 nm. Using a computer simulation, the researchers calculated the energy transfer rate constant to be 5 x 1010 for the third dye, which has pyrene and perylene groups. Although the dyes have similar properties, the pyrene/perylene dye has a broader excitation spectrum and Stokes shift, so the scientists believe that the dye is the most suitable for biochemical applications. Their computer simulations suggested that they could generate an energy cascade with that dye, but they did not have the facilities to test their hypothesis.