Synthesis, Spectro-Electrochemical Properties and Photoreaction with O₂ of Lutetium Bis-ethyltetraazaporphyrin

The synthesis, spectroscopic and electrochemical properties of the Lu ( oepz ) 2 (oepz ≡ 2,3,7,8,12,13,17,18-octakis(ethyl)-5,10,15,20-porphyrazinato) complex are reported. The complex, as inferred from UV-vis spectra recorded at different concentrations, strongly aggregates in solution, the most likely association mode being dimerization. The complex shows a weak near-IR absorption (λ max = 834 nm) that is considerably blue-shifted compared with the near-IR absorption of bis(π-radical) lutetium analogues. The Lu ( oepz ) 2 neutral species is electrochemically stable between 0.73 and -0.98 V (vs Ag/AgCl), which is the largest range of stability for neutral lutetium di- tetrapyrrole complexes. Lu ( oepz ) 2 shows excellent Type II photodynamic activity, as indicated by the value of the singlet oxygen generation quantum yield φ Δ of 0.94 obtained by comparison with meso-tetraphenylporphyrin.