Optimally tuned functionals improving the description of optical and electronic properties of the phthalocyanine molecule

By means of Density functional theory and time-dependent density functional theory calculations, we present a comprehensive investigation on the influence of different functional schemes on electronic and optical properties of the phthalocyanine molecule. By carrying out our own tuning on the OT-LC-BLYP/6-31G(d,p) functional, we show that such a procedure is fundamental to accurately match experimental results. We compare our results to several others available in the literature, including the B3LYP/6-31+G(d,p) set, which is commonly portrayed as the best combination in order to obtain a good description of the band gap. The results obtained here present not only significant improvement of the optical properties from the conventional BLYP, but we can also objectively report an improvement of our tuned functional when compared to the current benchmark of the literature as far as optical properties are concerned. Particularly, by means of this approach, it was possible to achieve a good agreement between the theoretical and experimental optical gap as well as the positioning of the main peaks in the absorption spectrum. Our results thus suggest that correcting the long-range term on exchange term of the Coulomb operator, by means of a tuning procedure, is a good option to accurately describe properties of the phthalocyanine molecule.