Synthesis of 1-phenyl-3-biphenyl-5-(N-ethylcarbazole-3-yl)-2-pyrazoline and its use as DNA probe

A novel pyrazoline derivative, named 1-phenyl-3-biphenyl-5-(N-ethylcarbazole-3-yl)-2-pyrazoline, was synthesized, and its structure was confirmed by means of IR, 1H NMR, and elementary analysis. The compound emits strong yellow fluorescence. Decrease of fluorescence intensity of the pyrazoline derivative in the presence of calf thymus DNA (ct DNA) is observed, and the quenching obey Stern–Volmer equation. There is a single quenching mechanism for the complex, which belongs to static quenching. KI quenching study shows that the magnitude of KSV of the bound pyrazoline is lower than that of the free one. It is also found that ionic strength could affect the interaction. Binding constants for pyrazoline with ct DNA and salmon sperm DNA (ss DNA) are in the same order of 104 mol L−1, and binding site size are about 1 per base pairs. Experimental results indicate that the new compound might insert into DNA base pairs by intercalative binding mode.