Effect of Deprotonation and Reduction on the Molecular Structure and Optical and Magnetic Properties of Metal‐Free Phthalocyanine (Pc): Comparison of H 2 Pc .− and HPc − Anions

A method for the selective preparation of mono‐deprotonated phthalocyanine (HPc − anions) was developed, enabling the synthesis of crystalline [(Na + )(2.2.2‐cryptand)][HPc − ]⋅1.5 C 6 H 4 Cl 2 ( 1 ). Salt  1 is isostructural to the salt obtained by reduction, [(Na + )(2.2.2‐cryptand)][H 2 Pc .− ]⋅1.5 C 6 H 4 Cl 2 , containing the H 2 Pc .− radical anions. The phthalocyanine macrocycle in 1 shows no alternation of the C−N(imine) bonds that characterizes H 2 Pc .− . The spectrum of 1 does not feature near‐IR bands, and blueshifts of the Soret and Q bands characteristic of H 2 Pc .− were also not observed. Reduction shortens the N−H bonds, whereas deprotonation essentially elongates that bond with the remaining hydrogen atom. Deprotonated HPc − anions are EPR‐silent and diamagnetic, whereas H 2 Pc .− radical anions are paramagnetic and have the S = 1 / 2 spin state. These data indicate essential differences in the molecular structures as well as optical and magnetic properties of the deprotonated (HPc − ) and reduced (H 2 Pc .− ) phthalocyanine macrocycles.