Time-dependent density functional theory studies of the electronic absorption spectra of metallophthalocyanines of group IVA

Time-dependent density functional theory (TD-DFT) calculations were carried out in a comparative study of the electronic absorption spectra of lead(II) phthalocyaninate (PbPc), tin(II) phthalocyaninate (SnPc), tin(IV) dichlorophalocyaninate (PcSnCl₂), germanium(II) phthalocyaninate (GePc), and germanium (TV) dichlorophalocyaninate (PcGeCl₂) with the B3LYP method and LANL2DZ basis set. Our calculated bands correspond well with the experimental results. The electronic natures of all the bands in the absorption spectra are assigned and analyzed comparatively according to the calculated electronic transition contributions. With the increase of the dielectric constant from CHCl₃, to DMSO, all the electronic absorption bands are somewhat red shift, consistent with the shift rules measured experimentally. The radius of the central metals has great influence to the absorption spectra, especially for the B bands. The influence of the radius of the central metals to the absorption spectra of PcSnCl₂ and PcGeCl₂ is smaller than to the spectra of the nonplanar MPcs (M = Pb, Sn, and Ge). Axial ligands also greatly changed the electronic absorption spectra due to the change of the orbital energy level and the molecular symmetry.