Metalated porphyrins and phthalocyanines on surfaces: potential for environmental and energy applications Sivanujan Suthaharan Department of Chemistry, Illinois State University, USA
Porphyrins are planar aromatic molecules comprising a core tetrapyrrolic macrocycle. Molecular functionalization of the porphyrins has become significant in synthetic chemistry, molecular electronics, and surface science. High symmetrical D 4 h nature of metalated porphyrins is of great interest in the perspective of two-dimensional assemblies on surfaces and three-dimensional frameworks. Most of the transition metal elements can be incorporated into the core macrocycle [1,2] . Such complex systems are widely investigated in the context of higher order or dimensional arrangement of functionalized adsorbates on surfaces. Recent investigations on thermodynamic self-assembly of porphyrins are significant in illustrating the behavior of substrates on metallic surfaces. Functionalized porphyrin species are advantageous for photocatalysis, degradation, energy conversion and storage, and metal pollutant detection [3,4] . The applications of surface-deposited porphyrin species are not widely investigated. This would serve as a potential mechanism for efficient surface processes for environmental and energy applications. In this study, porphyrins with metal centers Ni, V, Cu and Co and phthalocyanines (Pc) adsorbed to gold (Au111) and highly ordered pyrolytic graphite (HOPG0001) surfaces are investigated. Favorable binding sites of metal-centered octa ethyl porphyrins (MOEP) and Pc on the surfaces are investigated. Further, adsorption energy trends with different metal centers, surfaces and binding sites and orbital-hybridization driven charge redistribution are investigated based on quantum mechanical density functional theory-level calculations. Density of states of isolated MOEP, Pc and MOEP/ Pc - Surface systems provide insights on energy level alignment. This study aims to demonstrate a systematic and comparative analysis of the adsorbate - surface interactions in terms of substrate conformations, energy level alignment, local electronic structure and charge redistribution employing periodic DFT calculations. References 1. Hiroto, S.; Miyake, Y.; Shinokubo, H. Synthesis and Functionalization of Porphyrins through Organometallic Methodologies. Chem. Rev. 2017 , 117 (4), 2910–3043. https://doi.org/10.1021/acs.chemrev.6b00427. 2. Chilukuri, B.; Mazur, U.; Hipps, K. W. Structure, Properties, and Reactivity of Porphyrins on Surfaces and Nanostructures with Periodic DFT Calculations. Applied Sciences 2020 , 10 (3), 740. https://doi.org/10.3390/app10030740. 3. Pathak, P.; Zarandi, M. A.; Zhou, X.; Jayawickramarajah, J. Synthesis and Applications of Porphyrin-Biomacromolecule Conjugates. Front. Chem. 2021 , 9 , 764137. https://doi.org/10.3389/fchem.2021.764137. 4. Chilukuri, B.; Mazur, U.; Hipps, K. W. Effect of Dispersion on Surface Interactions of Cobalt( ii ) Octaethylporphyrin Monolayer on Au(111) and HOPG(0001) Substrates: A Comparative First Principles Study. Phys. Chem. Chem. Phys. 2014 , 16 (27), 14096–14107. https://doi.org/10.1039/C4CP01762E.
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