The search for efficient synthetic hosts able to encapsulate fullerenes has attracted attention with regard to the purification and formation of ordered supramolecular architectures. This study of a porphyrin-based cage as an extension of the well-described ExCage 6+ and BlueCage 6+ , involving viologen as sidearms, provides an interesting scenario where the oblate C 70 fullerene is preferred in comparison to the spherical C 60. Our results expose the nature of the fullerene-cage interaction involving $50% of dispersion-type interactions evidencing the strong πÁ Á Áπ surface stacking, with a complementary contribution by the electrostatic and orbital polarization character produced by a charge reorganization with a charge accumulation facing the porphyrin macrocycles and a charge depletion along the equator formed by the viologens sidearms. Interestingly, the central N 4 H 2 ring from each porphyrin contributes to the dispersion term via N-HÁ Á Áπ interactions, which is decreased when the metallate N 4 Zn is evaluated. Thus, the formation of stable and selective fullerene encapsulation can be achieved by taking into account two main driving forces, namely, (a) the extension of the πÁ Á Áπ and X-HÁ Á Áπ stacking surface and (b) charge reorganization over the fullerene surfaces, which can be used to control fine tuning of the encapsulation thanks to the introduction of more electron-deficient and electron-rich groups within the host cage. K E Y W O R D S fullerenes, host-guest, non-covalent interactions, porphyrin 1 | INTRODUCTION Fullerenes and their derivatives have attracted extensive attention since buckminsterfullerene (C 60) characterization [1-4] owing to their unique physicochemical properties, which are useful in a wide range of applications in material science. [5-7] Despite their relevant role, improved isolation and purification approaches are still required to achieve large-scale quantities. In this sense, selective encapsulation of fullerenes offers a key strategy in their purification after obtention methods, given by hydrocarbon combustion [8] and sublimation of carbon soot [9] among others. [10] It has been shown that the efficient and selective recognition of fullerenes can be achieved via host-guest pair formation owing to intermolecular interactions. [11,12] Currently, different molecular receptors have been used, involving bowl-like species [13-15] and cages, [16,17] where the nature of the host-guest formation is of particular importance for efficient fullerene encapsulation.
In the context of copper corrosion passivation, the adsorption of benzotriazole (BTAH) and its derivatives: 5-Methyl, 5-Amine, 1-Amine, 1-Methyl on a Cu(111) surface was investigated using periodic density functional (DFT) calculations. The results were contrasted with experimental ASTM protocols. Adsorption of BTAH and radical (BTA•) forms, as well as solvent effect were evaluated. The Cu-N interaction provides stable complexes with adsorption over top sites. Radical forms yielded more stable complex. Their adsorption energies correlate with the substituent position and electronic features. And finally, a strong interaction was obtained when the charge transfer goes from surface to adsorbate.
Superatomic clusters offer useful templates displaying distinctive physical and chemical characteristics. Here, we explore the [M@Au 8 (PPh 3 ) 8 ] n+ (M = Au, n = 3; Pd, Pt, n = 2) robust framework to gain an understanding of the nature of the inclusion of mercury atoms at Au 4 faces, leading to [M@Au 8 Hg x (PPh 3 ) 8 ] n+ (x = 1, 2). Our results show a weak interaction of about 25 kcal mol −1 per Hg atom, which is mainly of electrostatic character, followed by orbital and London dispersion-type interactions. This weak interaction can be understood as the formation of host-guest species, for which the inherent electronic and optical properties of the [M@Au 8 (PPh 3 ) 8 ] cluster along the series do not vary to a large extent. This demonstrates that, in [M@Au 8 Hg x (PPh 3 ) 8 ], each Hg can be considered an inclusion atom rather than a dopant element, where the parent cluster is able to act as a Lewis acid host. Furthermore, the viable formation of such species can serve as useful examples to stimulate future experimental characterization of inclusion complexes involving related superatomic structures with available open faces. K E Y W O R D S clusters, gold clusters, Lewis-acid, mercury
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