Combined molecular and periodic DFT analysis of the adsorption of co macrocycles on graphene

Abstract

The molecular doping of graphene with π-stacked conjugated molecules has been widely studied during the last 10 years, both experimentally or using first-principle calculations, mainly with strongly acceptor or donor molecules. Macrocyclic metal complexes have been far less studied and their behavior on graphene is less clear-cut. The present density functional theory study of cobalt porphyrin and phthalocyanine adsorbed on monolayer or bilayer graphene allows to compare the outcomes of two models, either a finite-sized flake of graphene or an infinite 2D material using periodic calculations. The electronic structures yielded by both models are compared, with a focus on the density of states around the Fermi level. Apart from the crucial choice of calculation conditions, this investigation also shows that unlike strongly donating or accepting organic dopants, these macrocycles do not induce a significant doping of the graphene sheet and that a finite size model of graphene flake may be confidently used for most modeling purposes. © 2017 Wiley Periodicals, Inc.

Different Pathways for CO2 Electrocatalytic Reduction by Confined CoTMPyP in Electrodeposited Reduced Graphene Oxide

“…Establishment of a close proximity between some of the carboxyl groups and the active metal ion center in the porphyrins seems to be plausible for rGO-CoTMPyP and rCGO-CoTMPyP since these have been characterized as coatings with a considerable concentration of −COOH groups (content of at least ∼2%), a dense population of porphyrin molecules (multilayered surface coverage of 8.1 × 10 –9 mol cm –2 ), and strong π–π stacking graphene-porphyrin interactions. These interactions are expected to lead to close interplanar separation which has been estimated to be in the 3–5 Å range for graphene-porphyrin systems. , Similar considerations (including axial ligation) have been suggested for a pyridyl-related proton relay mechanism in cobalt phthalocyanine encapsulated in polymeric 4-vinylpyridine coatings . Two CO 2 RR pathways leading to the formation of CO and to formate, as described, are therefore related to the extent of proximity between the proton relays and the cobalt ion centers: distant sites leading to CO while close ones promoting the formation of a Co­(hydride)­porphyrin intermediate which reacts with CO 2 to produce formate.…”

“…These interactions are expected to lead to close interplanar separation which has been estimated to be in the 3−5 Å range for graphene-porphyrin systems. 56,57 Similar considerations (including axial ligation) have been suggested for a pyridyl-related proton relay mechanism in cobalt phthalocyanine encapsulated in polymeric 4-vinylpyridine coatings. 58 Two CO 2 RR pathways leading to the formation of CO and to formate, as described, are therefore related to the extent of proximity between the proton relays and the cobalt ion centers: distant sites leading to CO while close ones promoting the formation of a Co(hydride)porphyrin intermediate which reacts with CO 2 to produce formate.…”

DFT Quantum-Chemical Modeling Molecular Structures of Cobalt Macrocyclic Complexes with Porphyrazine or Its Benzo-Derivatives and Two Oxygen Acido Ligands

“…These complexes are interesting in that, as it is easy to see from these formulas, in any of these complexes the cobalt atom is bonded to other atoms by eight chemical bonds, six of which are formed by the exchange mechanism (namely, two with each of two oxygen atoms and one with the each of two nitrogen atoms), and according to the generally accepted definition, the concept of "oxidation state", the value of this parameter for a given atom of a 3d-element should be accepted equal to (+6). It should be specially noted that no mention of complexes of type I-III in the special literature devoted to (NNNN)-donor atomic macrocyclic ligands-porphyrins, porphyrazines and their derivatives [14][15][16][17][18][19][20][21][22], or anywhere else, could not be found. In this connection, the given article will be devoted to a theoretical analysis regarding the possibility of the existence in principle of such complexes with the use of modern methods of quantum chemistry, namely, the density functional theory (DFT) method.…”

Modeling the roles of rigidity and dopants in single-atom methane-to-methanol catalysts

“…2,32,[34][35][36][37] Additionally, PBCs may enforce unnecessary symmetry and rigidity in the metal-local environment in disordered SACs, which are known to exhibit curvature. 27 Finite models, 38 conversely, are more tractable for higher-cost methods (e.g., range-separated GGA hybrid functionals) that suffer less from delocalization error. The extent to which nite-size effects can inuence predictions of SAC properties remains unclear.…”