Aromatic character of O_h‐C₂₄N₂₄. A cavernous nitride fullerene bearing N₄‐macrocycle motifs

Abstract

Spherical fullerenes offer noteworthy structures usually involving six-and fivemembered faces, with application in technological issues. In this sense, cavernous spherical-like structures bearing larger holes provide interesting examples for further understanding of structure-properties relationship. Here, we explored the magnetic response of a proposed cavernous nitride fullerene, C 24 N 24 , which has a O h -symmetry with six N 4 -macrocyclic and eight 1,3,5-triazine faces displaying 48-π electrons. C 24 N 24 exhibits a local aromatic behavior owing to the contrasting antiaromatic response of the N 4 -macrocyclic faces and the aromatic character of the 1,3,5-triazine faces. Thus, the overall structure is ascribed as a local aromatic species, where the triazine faces exhibit the characteristic shielding cone for aromatic rings. Furthermore, the constructive combination of local shielding cones in C 24 N 24 delivers a related shielding-cone response, as expected for a perfect aromatic cage. Hence, the local aromatic/nonaromatic/antiaromatic sections exhibit an additive or subtractive interaction, leading to a characteristic response inherent to the nature of the spherical cage. We expect that further study of the interplay between different aromatic and antiaromatic faces in fullerene-like cages can deliver interesting pseudo-aromatic or pseudo-antiaromatic spherical species. K E Y W O R D S aromaticity, cavernous, fullerene, magnetic fields | INTRODUCTIONFollowing the seminal discovery of buckminsterfullerene, [1][2][3] the field of related spherical structures has attracted interest from scientific community, resulting in an extensive and continuous growth of practical interdisciplinary applications with technological concerns. [4][5][6][7][8][9] C 60 , a spherical cage belonging to the icosahedral point group with sixty chemically equivalent sp 2 carbon atoms, provides a hollow structure with a high surface area, which is desirable for applications in lithium-ion batteries, [10][11][12] catalyst supports, [13,14] hydrogen storage, [15] solar cells, [16] and drug and gene delivery [5] , among others.Further surface modification of fullerenes by the so-called molecular surgical method [17][18][19] allows generating an open hole with the capability to including guest species, before the enclosure of the cavity. A similar structure has been proposed by Sundholm, [20,21] on the basis of Gaudi's architecture motifs, displaying an interesting cavernous structure with six open faces involving 72-π electrons coined as Gaudiene (O h -C 72 ).Despite the sizable cavities, it exhibits a spherical aromatic character given by the characterization of the magnetic response upon an external field from different orientations and follows a favorable electron count fulfilling the Hirsch's 2(N + 1) [2] rule for spherical aromatic species with N = 5. [22][23][24][25]

The σ+π dual aromaticity of typical bi‐tetrazole ring molecule TKX‐50

“…Over time, a multitude of compounds analogous to aromaticity has been found, which has automatically led to a concomitant proliferation of methods and theories to clarify these different characteristics sometimes found in very different compounds. These compounds range from the initial com-pound benzene and its analogs [10,11] to cyclenes, [12][13][14] to various heterocyclic organics, [15][16][17][18][19][20][21][22][23][24] to inorganic compounds [25][26] and Metalla-aromaticity, [27][28][29][30] note here that we mention only some literature on the grounds of too many. According to research on these various aromatic compounds, too many types of aromaticity were defined such as Hückel aromaticity, Möbius aromaticity, Baird aromaticity, σ-aromaticity, π-aromaticity, δaromaticity, multiple aromaticity, excited state aromaticity, transition state aromaticity, three-dimensional aromaticity, spherical aromaticity, cubic aromaticity, octahedral aromatic-ity…, here to mention a few.…”

Enhanced electronic and nonlinear optical responses of C24N24cavernous nitride fullerene by decoration with first row transition metals; A computational investigation

“…[ 48 ] This fullerene has six N4 cavities, which are similar to those appear in porphyrine. [ 49 ] These cavities are active sites to host metals by the formation of strong metal‐N covalent bonds. Moreover, several reports have been suggested that metal‐coordinated C 24 N 24 fullerenes show significant catalytic activity toward some reactions.…”