Synthesis of subphthalocyanine derivatives with annulated heterocyclic rings

Subphthalocyanines are emerging as highly versatile chromophores with potential applications in nonlinear optics, energy and electron transfer systems, light-emitting diodes, anion sensing, and supramolecular chemistry (1, 2). Subphthalocyanine derivatives are used as reagents for the ring enlargement reaction to prepare unsymmetry phthalocyanine derivatives (3). On the other hand, nitrogen and sulfur containing aromatic heterocyclic compounds, called benzothiazole and its derivatives, are very important species (4). In view of the biological importance of both benzothiazoles and subphthalocyanines, it is worthwhile to combine these two funcional structures into a single compound.

Novel derivatives of subphthalocyanine with annulated thiazole rings have been designed, synthesized and characterized. The effect of fused thiazole rings with the acceptor character on the periphery macrocycle on the electronic absorption spectra is examined.

Subphthalocyanines were obtained as a mixture of structural isomers with the point group symmetry C₃ and C₁ by cyclotrimerization reaction of corresponding dinitrile precursors in the presence of boron trihalide. The key dinitriles were prepared via some multi-step synthesis, starting with commercially available 4-aminophthalonitrile. Subphthalocyanine derivatives are soluble enough in some organic solvents to allow the study of their photophysical properties by means of absorption and fluorescence spectroscopy, together with their analysis by NMR.