Phthalocyanines and Porphyrins

Phthalocyanines (Pcs) are the synthetic analogues of the naturally-existing porphyrins (P), containing four aza-nitrogens instead of the four meso-carbons of the porphyrin system. The Pc macrocycles contain a 18π electron system which is a feature that contributes to their remarkable thermal and chemical stability. It is also the basis for their varied photophysical and semiconducting properties. They possess 16 potential functionalisation sites at the periphery and their central cavity can accommodate  >100 different metallic cations.

 

My first research post was a project scientist at York University under the supervision of Clifford C. Leznoff led to my introduction to the field of  Phthalocyanines. This project was purely synthetic and involved nucleophilic substitution reactions of hexadecasubstituted phthalocyanines.

I was quite keen to continue working with Pc materials, so I applied to the University of East Anglia (UEA) where I started my PhD studies under the supervision of Michael J. Cook (2007-2012) and Andrew N. Cammidge (2008-2012).  It was here that I specialised in the synthesis of peripheral (p) and non-peripherally (np) substituted phthalocyanine derivatives. During this time, a major breakthrough in the synthesis of phthalocyanine-like compounds was achieved within the group in which a semi-controlled synthetic procedure for selectively obtaining phthalocyanine-porphyrin hybrids (tetrabenzoazaporphyrins) was developed. Five tetrabenzo(aza)porphyrin derivatives can be obtained by replacing the aza-nitrogens on the Pc core by meso-carbons.

This accomplishment allowed us to optimise further the synthesis, isolation and characterisation of a series of novel tetrabenzoazaporphyrin derivatives. Unlike phthalocyanines these materials had not been the subject of thorough study, and up until 2011 less than a hundred papers and patents concerning these compounds had been written. The research on this subject generated several publications including a chapter in The Handbook of Porphyrin Science.

 

(Left to right) Phthalocyanine, tetrabenzo(triaza)porphyrin, trans- and cis-tetrabenzo(diaza)porphyrin, tetrabenzo(monoaza)porphyrin and tetrabenzoporphyrin

 

Isolation of these derivatives proved challenging but was successfully achieved for the first time for all of the analogues, including both cis- and trans-TBDAP isomers. In addition, their full characterisation allowed insight into the effects of structural modification of the core of the macrocycle as their optical and physical properties displayed significant differences. For the interest of the PhD research project, lead and copper (II) salts were used for metallation.  The series of Cu-hybrids were studied by MCD spectroscopy by Dr. John Mack in collaboration with Prof. Nagao Kobayashi in Tohoku University (Japan). Results of the studies in addition to the first DFT theoretical analysis were published shortly thereafter giving once again the first reports on the derivatives series and also corroborated the existing predictions of their electronic properties first calculated in the 1940’s.

Another part of the PhD research involved the design and provision of lead phthalocyanine materials for the development of an organic memory device in collaboration with the Ray Group (then at Queen Mary University of London, now at Brunel University) and three other small and medium enterprises (Opsec).

Other work I developed concerning lead phthalocyanines were to study of the effects of the chain length and position in a series of alkyl substituted lead phthalocyanines and their influence in the lead cation’s lability by the use of NMR spectroscopy. It was found that the lead cation within each of the peripherally substituted octaalkyl lead phthalocyanines was more labile than that in the non-peripherally substituted isomer. This was confirmed later on by XRD studies of single crystals which clearly show the de-formation of the Pc aromatic core in the p-Pcs vs the surprisingly planar np-Pc as shown below.

 

 

PUBLICATIONS on this TOPIC

 

Phthalocyanine analogues: unexpectedly facile access to non-peripherally substituted octa-alkyl tetrabenzotriazaporphyrins, tetrabenzodiazaporphyrins,  tetrabenzomonoazaporphyrins and tetrabenzoporphyrins, I. Chambrier, M. J Cook, A. N. Cammidge, D. L. Hughes, M. Rahman, L. Sosa Vargas, Chem. Eur. J., 2010, 17, 3136 – 3146.

 

Synthesis, characterisation, MCD spectroscopy and TD-DFT calculations of copper metallated non-peripherally substituted octa-octyl derivatives of tetrabenzotriazaporphyrin, cis and trans tetrabenzodiazaporphyrin, tetrabenzomonoazaporphyrin and tetrabenzoporphyrin J. Mack, L, Sosa-Vargas, S. J. Coles, G. J. Tizzard, I. Chambrier, A. N. Cammidge, M. J. Cook, Kobayashi, N. Inorg. Chem. 2012, 51, 12820-12833.

Synthesis and Properties of the Hybrid Phthalocyanine-Tetrabenzoporphyrin Macrocycles A. N. Cammidge, I. Chambrier, M. J. Cook and L. Sosa-Vargas, Handbook of Porphyrin Science Vol. 16, 2012, K. M. Kadish, K. M. Smith, R. Guilard (Eds.) World Scientific, 331-404.

 

Synthesis and characterization of some octaalkyl substituted lead phthalocyanines and unexpected variations in lead lability arising from the position of substituents and their chain length L. Sosa-Vargas, I. Chambrier, C. J. MacDonald, S. J. Coles, G. J. Tizzard, A. N. Cammidge, M. J. Cook  J. Porphyrins and Phthalocyanines, 2013, 17, 511-521.

Hybrid phthalocyanine/lead sulphide nanocomposite bistable memory switch Z. Khozaee, L. Sosa-Vargas,   A. N. Cammidge, M. J. Cook, A. Ray, Mater. Res. Express, 2015, 2, 096305.

Charge transport in lead sulfide quantum dots/phthalocyanines hybrid nanocomposites C. Pal, L. Sosa-Vargas, J. J.Ojeda, A. K. Sharma, A. N. Cammidge, M. J. Cook, A. K.Ray. Org. Electron. 2017, 44,132-143.

 

BACK TO RESEARCH

 

Cammidge group 2011
Cook group 2007

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