Synthesis and Properties of Saddle‐Distorted α‐Octa‐Substituted Metal‐free Phthalocyanines

Structurally distorted octa‐substituted metal‐free phthalocyanines (Pcs) substituted with alkyl or aryl groups at the α‐positions were synthesized and their properties were studied. Structural optimization calculations suggested that the saddle‐type distorted structures are the energetically most favorable for these compounds, although other structures such as the ruffled structure may be possible depending on the initial structure adopted, presumably due to the greater structural repulsion between substituent groups. A clear co‐relationship was found between the extent of saddle type distortion and the ease of diprotonation of pyrrole nitrogen: our analysis showed that the higher the distortion, the easier the diprotonation of the pyrrole nitrogen becomes. By comparing the experimental and calculated/simulated absorption spectra, it is concluded that the configuration interaction is larger for phenyl‐substituted Pcs than for alkyl‐substituted Pcs, which seems to be one of the reasons why the Q band of phenyl‐substituted Pcs appears at longer wavelengths.