Synthesis, spectroscopic/electrochemical characterization and DNA interaction study of novel ferrocenyl‐substituted porphyrins

We report the synthesis and characterization of two new meso-ferrocenylporphyrins, with the ferrocenyl unit attached at the para position of a C6F4 group by a CN bond with NH(CH2)2NH (2a) and NH(CH2)4NH (2b) spacers. Compounds 2a and 2b were characterized through elemental analyses, electrospray ionization high-resolution mass spectrometry, 1H NMR, UV–visible and fluorescence spectroscopies, electrochemistry and spectroelectrochemistry. The free base porphyrin 2 was included for comparison purposes. The binding ability of 2 and the porphyrin derivatives 2a and 2b with calf thymus DNA was determined using UV–visible and fluorescence spectroscopies. The results suggest that the interaction of these systems most probably occurs through π-stacking by non-classical modes involving the partial insertion of the C6F5 ring between adjacent base pairs on DNA and possible hydrogen interaction with the aliphatic NH(CH2)nNH (n = 2 or 4) groups with calf thymus DNA. Moreover, we also demonstrate that porphyrins generate singlet oxygen species and show good photostability after irradiation.