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 of 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.

Phthalocyanines represent a crucial class of organic compounds with high technological appeal. By doping the center of these systems with metals, one obtains the so-called metal-phthalocyanines, whose property of being an effective electron donor allows for potentially interesting uses in organic electronics. In this sense, investigating optical and electronic structure changes in the phthalocyanine profiles in the presence of different metals is of fundamental importance for evaluating the appropriateness of the resulting system as far as these uses are concerned. In the present work, we carry out this kind of effort for phthalocyanines doped with different metals, namely, copper, nickel, and magnesium. Density functional theory was applied to obtain the absorption spectra, and electronic and structural properties of the complexes. Our results suggest that depending on the dopant, a different level of change is achieved. Moreover, electrostatic potential energy mapping shows how the charge distribution can be affected by solar radiation. Our contribution is crucial in describing the best possible candidates for use in different organic photovoltaic applications. Graphical Abstract Representation of meta-phthalocyanine systems. All calculations of this work are based on varying metal position along z axis, considering the z-axis has its zero point matching with the center of phthalocyanine cavityconsidering.

Organic compounds, such as metallophthalocyanines (MePc), have emerged as important candidates to be used as active materials in numerous applications in Organic Electronics. Several studies have addressed the impact of the position of the central metal atom relative to the organic cage of the phthalocyanine (Pc) and the possibility of exploiting it in numerous applications. Pcs are sensitive to the presence of substances such as carbon dioxide (CO 2 ) and ammonia (NH 3 ) [1], for example, which allows the incorporation of this class of molecules in the development of chemical sensors for the identification of such substances. With the population and industrial growth in the last years, the emission of toxic gases in the environment has increased significantly, requiring a greater control of these compounds. In order to simulate how the ammonia sensor works, we extracted a NiPc crystal (nickel phthalocyanine) from the CCDC crystallographic database [2] and we used the Materials Studio computational package to add NH 3 molecules to a periodic box. We performed a Molecular Dynamics simulation in the system in order to identify how ammonia interacts with NiPc. We have employed the Density Functional Theory (DFT) to examine the structural, electronic and optical properties of the system. When the Pc molecule is exposed to the ammonia gas, the interaction between the gas and the metal center of the Pc presents a change in its conductivity [1]. The computational calculations indicated the interaction of the ammonia with the metallic center of the Pc, promoting a displacement out of the plane of the central metal (Ni), causing a loss of symmetry [3]. Our results support the hypothesis that the metal serves as a transfer channel between ammonia and NiPc. These data show that NiPc can be designed and used for sensing ammonia. This approach seems to be useful for the development of sensor arrays. Acknowledgments:The authors are grateful for the support given from the University of Brasilia and from the Brazilian Research Councils CNPq and CAPES.