Nature of C₆₀ and C₇₀ fullerene encapsulation in a porphyrin‐ and metalloporphyrin‐based cage: Insights from dispersion‐corrected density functional theory calculations

Abstract

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.

Boosting Photoelectric Conductivity in Porphyrin-Based MOFs Incorporating C60

“…The higher binding energy in F-MOF is consistent with the better aligned π–π stacking interactions between the porphyrin and C 60 in its case. Such strong C 60 binding energies are consistent with dispersion type interactions reported for fullerene-encapsulated porphyrin-based cage complexes …”

“…Such strong C 60 binding energies are consistent with dispersion type interactions reported for fullerene-encapsulated porphyrin-based cage complexes. 58 To understand the influence of C 60 incorporation, we have calculated the total density of states (TDOS) for DA-MOF and F-MOF before and after incorporation of C 60 (Figure 2). Calculated optical band gaps (E g ) for DA-MOF and F-MOF are 1.66 and 2.04 eV, respectively, which is in the visible region as expected for the porphyrin-based linkers.…”

Noble gas endohedral fullerenes

“… 88 The BP86 functional combined with dispersion correction (D3 or D3(BJ)) can also describe such systems. 89 Therefore, in general, any functional that takes into account short-range and/or long-range dispersion interactions or ab initio methods in combination with sufficiently large basis set would provide reliable energetics. 71 , 86 , 90 , 91 …”

Computational insights into the Multi-Diels-Alder reactions of neutral C60 and its Li+ encapsulated analogue: A DFT study

“…Among the experimental and theoretical methods implemented for fullerene modifications, Diels-Alder cycloaddition reaction [19][20][21][22][23] on the fullerene surface and encapsulation of atom/metal cluster/small molecules into the hollow cage of fullerene [24][25][26][27] are drawing great scientific attention. In this aspect, selective encapsulation of fullerene cages is also observed to offer one of the key techniques in their purification [28 ] . On the I h -symmetric C 60 , mainly two kinds of C-C bond connectivity [29 ] have been observed, namely [6,6] and [6,5].…”