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 C-N bond with -NH(CH2)(2)NH- (2a) and -NH(CH2)(4)NH- (2b) spacers. Compounds 2a and 2b were characterized through elemental analyses, electrospray ionization high-resolution mass spectrometry, H-1 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 U V-visible and fluorescence spectroscopies. The results suggest that the interaction of these systems most probably occurs through pi-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)(n)NH- (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.