Juri Mai

Phthalocyanines (Pc), which in general are widely used as blue and green pigments in paper and textile industries, consist of a planar macrocycle with an extended 18 π-electron system and possess intense absorption around 700 nm (Q band) and a second absorption near 350 nm (B band), with almost no absorptivity in between. For additional applications in materials science, e. g. as photosensitizers in solar cells, it is necessary to expand the absorption profile, since it greatly affects the efficiency of such organic devices. Thus, closing the optical window can be achieved by multichromophore ensembles composed of phthalocyanines and a second class of dyes that absorb between 500-650 nm (e.g. BODIPY).

The central part of my work is the synthesis of an octaphenylphthalocyanine scaffold 1a with solubilizing t-butyl and eight halogen substituents in its periphery. Whereas the t-butyl groups prevent π-stacking and enhance the solubility of the phthalocyanine, the halogen substituents enable the convenient attachment of complementary absorbing chromophores (to close the optical window) via Pd-catalyzed C-C cross-coupling reactions.

Furthermore the oxidative coupling of the terphenyl substructure in 1a to phthalocyanine Pc 1b would induce a strong bathochromic shift of the Q-Band. These near IR absorbing chromophores 1a,b will be investigated and their electrochemical properties compared with the corresponding tetrapyrazinoporphyrazines that are explored in our group.

The key component for both phthalocyanines 1a,b is a dihalo-o-terphenyldicarbonitrile 2. It can directly be used for the cyclotetramerization reaction or it can be planarized via oxidative cyclodehydrogenation to triphenylene 3.

H. Thiede, F. Koerte, M. Kahlmeyer, J. Mai, R. Faust, S. Böhm, Monitoring and damage detection of adhesive bonds with micro-encapsulated markers Welding in the World, Springer, 2013.
DOI: 10.1007/s40194-013-0099-2