Gas‐Phase Electronic Structure of Phthalocyanine Ions: A Study of Symmetry and Solvation Effects

Abstract Research into and applications of phthalocyanines (Pc) are mostly connected to their intriguing electronic properties. Here, messenger‐type UV–vis spectroscopy of two metal‐free ions from the phthalocyanine family, cationic H₂Pc⁺ and H₂PcD⁺, along with their hydrates is performed. They show that the electronic properties of both ions can be traced to those in the conjugate base, Pc^2–, however, they are affected by state splitting due to the reduced symmetry; in the H₂Pc⁺ radical cation, a new band appears due to excitations into the singly‐occupied molecular orbital. Quantum chemical spectra modeling reproduces all important features of the measured spectra and provides insight into the nature of electronic transitions. Hydration of the ions has only a mild effect on the electronic spectra, showing the stability of the electronic structure with respect to solvation effects.