Extending a porphyrin chromophore via fusion with naphthalene

An intramolecular oxidative aromatic coupling of meso-substituted porphyrins bearing electron-rich aromatics was the focus of investigation. The formation of C-C bond at beta-position for macrocycles bearing dimethoxynaphthalene moiety was achieved. It was established that Fe(ClO4)(3)center dot H2O induced only single cyclodehydrogenation whereas Fe(OTf)(3) had the ability to remove four hydrogens and four electrons forming doubly-fused porphyrin. Both Fe(ClO4)(3)center dot H2O and Fe(OTf)(3) were confirmed superior to FeCl3 as they ensured efficient oxidation process without concomitant chlorination of the products. We have proven that the trans-A(2)B(2)-porphyrin with two indole moieties do not form any stable products under such reaction conditions. The single fusion with dimethoxynaphthalene moiety has a comparable effect on absorption spectra i.e. the Q-band of Ni-complexes is shifted to 650 nm. The Niporphyrin fused with two naphthalene units had bathochromically shifted Q-bands to 733 nm.