Structural changes in non-planar octaaryl substituted phthalocyanine phosphorus complexes

Phosphorus complexes of non-planar alpha-octaaryl phthalocyanine derivatives ((alpha-Ar)(8)Pc), 3a and 3b have been synthesized by introduction of phosphorus(V) ions into free-base Pcs 2a and 2b. 3a and 3b were characterized by MS, H-1 and P-31 NMR spectra. The solid state structure of 3a indicated a ruffled Pc structure due to the small atomic radius of phosphorus, although the corresponding free-base Pc 2a has a saddled Pc structure. The phosphorus complexes showed intense absorption bands (Q-bands) in the near-IR region, while the introduction of electron-donating groups at the peripheral phenyl groups was efficient for additional red-shifting of the Q-band. Electrochemical data revealed that the red-shift of the Q-band is attributable to a decrease in the HOMO-LUMO gap due to significant and moderate stabilization of the LUMO and HOMO, respectively. MO calculations suggested that the phosphorus(V) ion intensified the electronic interaction between the peripheral aryl moieties and the Pc macrocyclic core.