Synthesis, electrochemical and spectroscopic studies of multidodecylated liquid crystalline phthalocyanine-ferrocenylethoxide conjugates for biochemical applications

This thesis is concerned with the synthesis and characterisation of some ferrocenyl and phthalocyanine derivatives. Symmetrically dodecylated phthalocyanines were obtained by the cyclisation of 3,6-bis(dodecyl)phthalonitrile. Unsymmetrically dodecyl-phthalocyanineferrocenylethoxide conjugates were obtained by the statistical condensation of 3,6-bis(dodecyl)- phthalonitrile and 4-(2'-ferrocenylethoxy)phthalonitrile. The anchoring of the ferrocenyl fragment, which itself is an antineoplastic entity, onto a phthalocyanine was accomplished utilising an ether bond. The electrochemical behaviour of the ferrocenyl and selected phthalocyanine derivatives is reported. Most of the ferrocenyl compounds undergo a one-electron reversible process. Four ring-based electron transfer processes for the metal-free phthalocyanines were observed, whereas the ferrocenyl-phthalocyanine conjugate showed an additional, fifth, redox couple associated with the ferrocenyl moiety. UV/VIS spectroscopy of the non-peripherally dodecyl substituted phthalocyanines showed a red shift in absorption Qmax-band, which holds some advantages for irradiation with low-energy diode lasers during photodynamic cancer therapy. The new phthalocyanines also obeyed the Beer-Lambert law for the concentration range 78-163 )µM (Q-band data) in THF, thus showing no aggregation. The new symmetrical octadodecylated phthalocyanines as well as the hexadodecylphthalocyanine- ferrocenylethoxide conjugates exhibited liquid crystalline mesophase behaviour, which was studied using polarised light optical microscopy and differential scanning calorimetry. The zinc-containing ferrocenyl-phthalocyanine conjugate displayed mesophase behaviour over a larger temperature range (30.9-269.9°C) than the metal-free conjugate (30.4-185.3°C). Variable temperature UVNIS spectra of thin films (ca. 1000 A thick) of the phthalocyanine derivatives cast on glass is also reported for each mesophase.