Photophysical and chemical processes controlling the fluorescence of anthraquinone-18-crown-5 derivatives.

摘要

Experimental and computational methods have been used to explore the photophysical and chemical causes of fluorescence and absorbance changes observed in anthraquinone-18-crown-5 derivatives upon the addition of select metal cations and the chemical reduction of the quinone. Time-dependent density functional theory (TDDFT) results suggest that anthraquinone-18-crown-5 and its chalcogen-substituted derivatives undergo internal charge transfer (ICT) upon excitation, and that the coordination of select metal cations to the internal carbonyl changes the energy of the excited charge transfer state. A pair of rhodamine-anthraquinone sensors have also been synthesized and investigated computationally and experimentally. Characterization by 1H NMR, 13C NMR, and single crystal x-ray diffraction (XRD) will be discussed. Fluorescence and absorbance spectra of these sensors is dependent on the oxidation state of the quinone, the concentration of select metal cations, the solvent mixture, and the kinetics of spirolactam ring opening, metal ion reduction, and ligand oxidation and/or degradation in solution.