Effects of Peripheral Substituents on the Electronic Structure and Properties of Unligated and Ligated Metal Phthalocyanines, Metal = Fe, Co, Zn.

The effects of peripheral, multiple -F as well as -C2F5 substituents, on the electronic structure and properties of unligated and ligated metal phthalocyanines, PcM, PcM(acetone)2 (M = Fe, Co, Zn), PcZn(Cl), and PcZn(Cl(-)), have been investigated using a DFT method. The calculations provide a clear explanation for the changes in the ground state, molecular orbital (MO) energy levels, ionization potentials (IP), electron affinities (EA), charge distribution on the metal (QM), axial binding energies, and in electronic spectra. While the strongly electron-withdrawing -C2F5 groups on the Pc ring change the ground state of PcFe, they do not influence the ground state of PcCo. The IP is increased by ∼1.3 eV from H16PcM to F16PcM and by another ∼1.1 eV from F16PcM to F48PcM. A similar increase in the EA is also found on going from H16PcM to F48PcM. Substitution by the -C2F5 groups also considerably increases the binding strength between PcM and the electron-donating axial ligand(s). Numerous changes in chemical and physical properties observed for the F64PcM compounds can be accounted for by the calculated results.