Electronic structures of zinc octaalkylthio- and octaphenylthio-tetrapyrazinoporphyrazines, and comparison with those of phthalocyanines and pyrazinoporphyrazines

Abstract

Eight strongly electron-donating alkylthio- or arylthio-groups have been introduced to a strongly electron-withdrawing pyrazinoporphyrazine (PyZ) core, to form the Zn complexes of octadecylthiolated ZnPyZ, (SDc)[Formula: see text]ZnPyZ, and octaphenylthiolated ZnPyZ, (S[Formula: see text])[Formula: see text]ZnPyZ, and their electronic structures studied by 1H NMR and electronic absorption spectroscopy. The strength of the ring current, aromaticity, and flow of charge were discussed by calculating the ring current, nucleus-independent chemical shift (NICS), and anisotropy of the current-induced density (ACID), respectively. Good agreement was seen for the results of these three calculations, demonstrating that a strong ring current of the macrocycle is produced when the aromatic ring fused to the tetraazaporphyrin core has a weaker diamagnetic ring current, [Formula: see text]. weaker aromaticity (negatively smaller NICS values). TD-DFT molecular orbital (MO) calculations succeeded in explaining the differences of the absorption spectra between these octathiolated ZnPyZs and those without thiolated groups. The singlet oxygen quantum yield in pyridine (0.62) of (S[Formula: see text])[Formula: see text]ZnPyZ was similar to that (0.61) of normal ZnPc.