Optical properties of metal phthalocyanines

In this study, optical properties of phthalocyanines of five metals, i.e., cobalt, nickel, iron, copper, and manganese, have been discussed in the energy (E) range of 1.5–4.1 eV. Utilizing the available data of refractive index (n) and extinction coefficient (k) of these materials in the literature, the related optical properties such as the real (ε₁), imaginary (ε₂) parts of the complex dielectric constant (ε), and reflectivity (R) are calculated. Interpretations for the energies corresponding to the peaks in ε₂ are explained in terms of the Penn gap (E _P). High-frequency dielectric constant (ε_∞) values corresponding to four models, i.e., the conventional Lorentz model, modified Lorentz model, relaxed Lorentz model, and the dual Lorentz model are used to determine E _P. It is found that the E _P values corresponding to the conventional and dual Lorentz models are in good agreement with the average of energy peaks in the R-E and the ε₂-E spectra. The oscillator energy (E ₀) and the dispersion energy (E _d) of these materials have been determined utilizing the Wemple–DiDomenico model. The calculated values of (a) E ₀ are generally in good agreement with the Penn gap E _P, the average of the energy peaks in the R-E and the ε₂-E spectra and (b) E _d are comparable to those in the literature for CoPc and NiPc.