We have synthesized and spectrally characterized a series of new luminescent lanthanide complexes based on linear and macrocycle polyaminocarboxylate chelates, covalently joined to an organic sensitizer 7-amino-4-methyl-2(1H-quinolinone (carbostyril 124). These complexes are luminescent with both terbium and europium and have millisecond lifetime, sharply-spiked emission spectra (<10 nm fwhm), large Stokes shifts (>150 nm), excellent solubility, moderate absorption (12 000 M–1 cm–1 at 327 nm), and high quantum yields for lanthanide emission. These characteristics make them useful alternatives to radioactive probes, to fluorescent dyes, and as donors in energy transfer experiments. A comparison of luminescence, intensity, spectra, lifetime, and number of coordinated waters is made. Net charge varies from —2 to neutral and water coordination number from 0.2 to 1.2. By comparison of lanthanide emission lifetimes with lanthanide chelates without sensitizer, it is shown that the sensitizer does not lead to nonradiative de-excitation and that the quantum yield for lanthanide emission is likely close to unity. Emission of terbium in all chelates is similar. With europium, the macrocycle chelates have enhanced far-red emission (700 nm) and one linear polyaminocarboxylate chelate, triethylenetetraaminehexaacetic acid, has 60% of its emission with europium in a sharply-spiked band around 617 nm with a full width at half-maximum of 3.3 nm. These chelates are the most efficient energy transfer donors yet synthesized. In imaging, they may make possible two-color detection with no spectral overlap and a single excitation wavelength, as well as the ability to discriminate against short-lived autofluorescence background.
ASJC Scopus subject areas
- Colloid and Surface Chemistry