Pyridyl β-ketoenols, pyrazoles and their zinc complexes: synthesis, photophysical properties, and DNA binding

induced circular dichroism (ICD) and competitive dye displacement assays. Uncyclized ligands L1 and L3 displayed no detectable DNA interaction. Cyclized L4 produced a strong positive ICD signal, consistent with minor groove binding, while L2 showed negligible binding. Zinc complexation enhanced DNA affinity with both L2-Zn and L4-Zn, displacing Hoechst-33258, confirming selective minor groove binding.