Spectroscopic research on the interaction of 2-(4-dimethylaminophenyl)-5-fluoro-6-(morpholin-4-yl)-1H-benzimidazole and calf thymus DNA

UV-Vis spectra of the aqueous solutions of 2-(4-dimethylaminophenyl)-5-fluoro-6-(morpholin-4-yl)-1H-benzimidazole (1) at different pH values revealed that compound I is a tertiary base, which can combine three protons. Through the non-linear least square method, the logarithm of the three accumulative protonation constants of compound 1, namely, 1g beta(1), 1g beta(2) and 1g beta(3), were determined to be 4.96 +/- 0.03, 5.72 +/- 0.07 and 7.95 +/- 0.10, respectively. UV-Vis and the steady-state fluorescence spectra indicated that a special interaction occurs between compound I and calf thymus DNA at the pH value of 3.40, of which the binding constant, K-b, is (2.30 +/- 0.10) x 10(4) mol(-1) (.) L. Compound 1 in the concentration range of 10(-8) to 1.2 x 10(-6) mol (.) L-1 has a potential application to the quantitative determination of DNA.