Synthesis and Photophysical, Electrochemical and Theoretical Study of Thi­azole-Annelated Phthalocyanines

Phthalocyanines with annelated thiazole rings were synthesised by cyclotetramerisation of benzothiazoledicarbonitriles. Three types of these dicarbonitriles with ortho-configuration were prepared from disubstituted anilines and their cyclisation led to all possible patterns of annelation in the phthalocyanine skeleton. Further substitution at the periphery of the macrocycle by methyl or tert-butyl substituents was realised to improve the solubility or to allow further derivatisation of target molecules. The characteristic UV/Vis spectral Q-bands were shifted to higher wavelengths (712–729 nm) because of the higher delocalisation, and fluorescence quantum yields increased compared with isoelectronic naphthalocyanines. Aggregation properties of the studied phthalocyanines were dependent on the type of isomer. The effects of the annelation pattern on the redox potentials were also investigated. Experimental data are compared with theoretical values obtained by DFT calculations.