Theoretical study on crystal polymorphism and electronic structure of lead(ii) phthalocyanine using model dimers†
Lead(II) phthalocyanine (PbPc) crystallises into two modifications of monoclinic and triclinic systems. In order to investigate the solid state electronic structures, we calculated three model dimers and two model trimers of PbPc using the M06 method of density functional theory (DFT). The geometries of these models for the crystal polymorphs were optimised, and the stability of each model was discussed along with the Gibbs free energy when comparing with the case of the triclinic system of tin(II) phthalocyanine. The optimised geometries of these models simulated well the molecular structures and orientations in the crystalline solids of PbPc. The time-dependent DFT (TD-DFT) calculation has been applied to these model dimers and trimers in order to investigate the excited states. The results also reproduced well the observed UV-vis spectra of PbPc in the solid state.