LUMINESCENCE STUDIES OF QUINIZARIN AND DAUNORUBICIN |
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Authors: | Rodger N Capps Martin Vala |
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Institution: | Department of Chemistry, University of Florida, Gainesville, FL 32611, USA |
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Abstract: | Abstract— The absorption and emission spectra of quinizarin (1,4-dihydroxy-anthraquinone) have been investigated in hydrocarbon and alcoholic solvents. Fluorescence spectra in 3 different Shpolskii matrices were recorded at 14 K. Vibrational analyses of these spectra revealed the presence of 3, 8, and 9 sites in octane, heptane, and hexane matrices, respectively. The fluorescence lifetime was found to be 6.5 ns in hexane and EPA. Fluorescence photoselection measurements in EPA (77 K) showed that the first 4 electronic transitions of quinizarin are polarized parallel, parallel, perpendicular, and parallel to the long molecular axis and can be assigned, in order of increasing energy, to 1B2, 1B2, 1A1 and 1B2 (ππ*)→1A1(C2v,) transitions, respectively. The fluorescent transition is assigned as 1B1 (ππ*)→1A1. The absence of phosphorescence is attributed to the intramolecular hydrogen bonding present which displaces the parent anthraquinone n →* states above the ππ* states, thereby rendering the intersystem crossing (S1-T1) radiationless pathway inefficient. Photoselection measurements on daunorubicin, a substituted quinizarin and known anticancer drug, revealed an absorption band polarization pattern identical to that of quinizarin. These results are in part at variance with assumptions used in previous work on the intercalation specificity of daunorubicin with DNA. |
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