Dicationic porphyrins bearing thienyl and pyridinium moieties: Synthesis, characterization, DNA interaction and cancer cell toxicity

A new series of trans-dicationic pyridinium porphyrins, 5,15-di(2/3-thienyl)-10,20-bis(3'/4'-N-methylpyridinium)porphyrins (5a-8a), and their copper(II) and zinc(II) derivatives were synthesized in good yield. The compounds were characterized by various spectroscopic methods, together with electrochemical and single crystal X-ray crystallographic studies. Additionally, we evaluated the DNA interaction abilities of the trans-dicationic porphyrins using IJV-Vis and fluorescence spectroscopic titrations and the results revealed that the porphyrins interact strongly with calf thymus DNA by the outside groove binding mode with self-stacking. The highest intrinsic binding constant of 2.90 +/- 0.2 x 10(6) M-1 was obtained for the freebase porphyrin (8a), containing 4-pyridinium and 3-thienyl moieties. The photocleavage experiments disclose that the porphyrins employ an( 1)O(2)-mediated mechanism in cleaving DNA. The dicationic porphyrins also show significant anticancer activities and the induced cell apoptosis was visualized by fluorescence imaging. (C) 2019 Elsevier Ltd. All rights reserved.