Effect of polyfluorination on self-assembling and electronic properties of thioalkyl-porphyrazines

The novel polyfluorinated thioalkyl-porfirazine 2,3,7,8,12,13,17,18-octakis(1,1,1,2,2,-3,3,4,4-nonafluorohexylthio)-5,10,15,20-21H,23H-porfirazine was synthesized to investigate the fluorine effect on self-aggregation, electrochemical, and spectral properties of this class of tetrapyrrole macrocycles. This compound showed an ordered and quite thermally stable columnar discotic mesophase, never seen in non-fluorinated symmetrically substituted “free-base” thioalkyl-porphyrazines, revealing a significant effect of fluorine on molecular self-assembling properties. An important effect of fluorination was also observed on the spectral and electrochemical properties of the molecule, giving rise to a hypsochromic shift in the 400–700 nm range of UV-vis absorption spectrum and to a marked cathodic shift of the reduction potentials in respect to the non-fluorinated analogs. DFT and TDDFT calculations has been undertaken to elucidate the origin of the observed behavior. Interestingly, HOMO, LUMO, and band-gap values together with its mesomorphic properties make this compound a promising material for organic photovoltaics.