Excited-state proton transfers in 9-aminoacridine carboxamides
- Iowa State Univ., Ames, IA (United States)
- Univ. of Auckland School of Medicine, Auckland (Australia)
Excited-state proton transfers have been investigated for several isomeric and homologous N-((dimethylamino)-alkyl)-9-aminoacridine carboxamides in a time-correlated single photon counting fluorescence study. The pH behavior of these DNA intercalators` steady-state absorption and fluorescence spectra has also been investigated. While the excited-state pK{sub a}* for removal of a proton from the singly protonated species is close to the ground-state pK{sub a} in the parent molecule 9-aminoacridine, the presence of the carboxamide substituent renders pK{sub a}* much lower than pK{sub a} for the corresponding deprotonation in the present compounds. This fact, along with the presence of an additional deprotonation site at the distal N atom of the side chain, endows these molecules with complex pH dependence in their excited-state kinetics. Triexponential model functions are generally required to fit the experimental fluorescence decays. The pH dependence of the component lifetimes and preexponential factors can be simulated with a kinetic model for sequential deprotonations involving four aminoacridine species in both the ground and fluorescing states. These results provide a baseline study for comparisons with these intercalators` excited-state kinetics in DNA. 37 refs., 12 figs., 2 tabs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 62464
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 21 Vol. 99; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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