Comparative Electrochemical Properties of Phthalocyanines Bearing Fc(CH2)n- and/or Alkyl Substituents in Non-Peripheral and/or Peripheral Positions.

Phthalocyanines and their metal complexes¹have been studied for their interesting chemical, electrochemical, thermal and photochemical properties as well as for the numerous applications they may be used for.   These include the vast domain of catalysis, as photosensitizers for photodynamic therapy of cancer, ink-jet printing components and in memory devices. The phthalocyanine macrocycle may be modified by introduction of redox-active moieties (here ferrocene) in peripheral or non-peripheral positions to append the existing macrocycle redox centers (usually four are observable in DCM as solvent).  Non-peripherally substituted long alkyl chains also influence the redox and other physical properties such as mesophase behaviour. 

It is well known that the redox properties of phthalocyanine macrocycles change depending on the type of metal that is coordinated in the macrocyclic cavity.   The tendency of cadmium macrocycles to oligomerise even to heptamers is less known.  Further changes in the redox properties of this macrocycle may be induced by systematically changing the “meso” or “outer” nitrogen atoms to CH ultimately to liberate a benzoporphyrin.  

In this presentation, the synthesis of the above compounds will be presented very shortly.  Thereafter, the influence that alkyl chain length (expressed as R = C₁₀H₂₁ – C₁₈H₃₇ above),² linker atom X = S or O, metallocenyl chain length ( n = 1 – 4), coordinated metal species, M, and the effect of axial dimerisartion and trimerisation of Cd complexes on especially the redox properties  of these  unique macrocycles will be highlighted and brief mention will be made of the mesophase behaviour these changes induce.   Electrochemical results obtained for the systematical conversion from phthalocyanine to benzoporphyrin will also be presented.   

References

1.   E. Fourie, J. C. Swarts, I. Chambrier, M. J. Cook, Dalton Trans., 1145-1154 (2009).

2.   J. C. Swarts, E. H. G. Langner, N. Krokeide-Hove, M. J. Cook, J. Mater. Chem., 11, 434-443 (2001).