Characterization of a series of far-red-absorbing thiobarbituric acid oxonol derivatives as fluorescent probes for biological applications

Abstract

Chromophores that absorb in the far-red region of the spectrum are increasingly being utilized for applications in the biosciences. We have synthesized and evaluated a novel series of fluorescent oxonols based on thiobarbituric acids containing aryl and heteroaryl substituents. The novel chromophores possess narrow absorption spectra (∼40-nm bandwidths), reasonable Stokes shifts (∼25nm), and quantum yields of up to 0.67 in organic solvents and 0.3 in aqueous solvents, with absorption wavelength maxima at 620-640nm. The spectral properties of the compounds are sensitive to base and exhibit a loss of far-red absorbance that is concentration and time dependent. Derivatives have been synthesized..