Regioregular Phthalocyanines Substituted with Bulky Donors at Non-Peripheral Positions

Three regioregular phthalocyanines (1–3) were synthesized selectively by the cyclic tetramerization of phthalonitriles bearing a bulky diarylamine substituent at the next position of nitrile. The steric repulsion at the tetramerization of bulky phthalonitriles allowed for the selective formation of regioregular phthalocyanines as confirmed by NMR and single crystal X-ray structural analyses. The absorption spectrum of 1 substituted with di(4-tert-butylphenyl)amine groups at the non-peripheral positions showed a non-split Q-band at 764 nm, which was redshifted by 83 nm compared with that of metal free phthalocyanine (H₂Pc). The TD-DFT calculation and electrochemical studies prove that the substitution of diarylamine groups at the α-positions effectively destabilizes the HOMO energy level, which causes a large redshift of the Q-band. Moreover, 1 can generate a one-electron oxidation species through chemical oxidation. The Q-band position of 2 bearing 4,4′-dimetoxyphenylamine units was further shifted by 10 nm compared with that of 1. In addition, 3 having carbazole units showed a small redshift of the Q-band relative to H₂Pc. The hole-mobility of 2 in thin film was determined to be 1.1×10⁻⁵ cm V⁻¹ s⁻¹ by using a space charge limited current method. A perovskite solar cell employing 2 as a hole-transporting layer gave an efficiency of 5.1 % under standard global 100 Wcm⁻² AM 1.5 G illumination.