Interaction between DNA and cationic metalloporphyrins in ionic liquid solutions

We studied the interaction of water-soluble cationic metalloporphyrins, pPy and TMPyP, with the DNA double helix in ionic liquid solutions using CD and absorption spectra. The dispersibility of their porphyrin complexes was improved by electrostatic interactions of the anions of the ionic liquid. In the case of Cu(II) and Zn(II) complexes, the pPy complexes with pyridinium cations attached to the meso-phenyl groups via methylene groups intercalated into the DNA double helix, while the compact TMPyP complexes with pyridinium cations at the meso-position could not interact with DNA. Thus, it was suggested that the solvation behavior by ionic liquids depends on the structure of the porphyrin and also affects its interaction with DNA. Neither Mn(III) complexes with axial ligands could interact with DNA, regardless of the presence of the ionic liquids, due to their steric hindrance.