Fullerene size controls the selective complexation of [11]CPP with pristine and endohedral fullerenes

Abstract

The ability of the carbon nanoring [11]cycloparaphenylene ([11]CPP) for coordinating fullerenes has been tested using a series of hosts, including the pristine fullerenes C60, C70, C76 and C78, the clusterfullerene Sc3N@C80, monometallic endofullerenes Y@C82 and Tm@C82, and dimetallic endofullerenes Y2@C82 and Lu2@C82. A systematic theoretical study employing dispersion corrected density functional methods has been carried out in order to explore the characteristics of the complexes and the strength of the interaction. Depending on the dimer, complexation energies span from around -36 kcal mol-1 with C60 to -53 kcal mol-1 with the C82 derivatives. Dispersion is the main stabilizing contribution in these dimers, so the molecules arrange to maximize the number of close interatomic contacts. Since most fullerenes can properly fill the cavity of the nanoring the stability of the complexes is pretty similar, with the exception of the smallest fullerenes. The complexes with endohedral fullerenes show similar stabilities in all cases studied, with no noticeable dependence on the nature of the endohedral species. The results obtained suggest that fullerenes larger than C76 could be selectively encapsulated by [11]CPP compared to smaller fullerenes.

Molecules under Pressure: The Case of [n]Cycloparaphenylenes

“…For further discussion, see Figures S12 and S13 and the respective text in the SI. Figure 11a shows an example of reversible shape deformation of [10]CPP through ovalization.…”

“…The unusual cyclic molecular symmetry of [n]CPPs offers a unique case of cyclic circulation of the −electron density, or cyclic −conjugation, which confers on them distinct optical and electronic properties governed by their increasing strain with decreasing n. 9 The −conjugated scientific community has been captivated by the circular aromaticity of [n]CPPs, their tunable size, varying degrees of aromaticity, unique sizedependent supramolecular properties, encapsulation of guest molecules and promising applications in material science. 10,11 Because [n]CPPs represent the shortest segments of armchair single wall carbon nanotubes (SWCNTs) 12 , they can also serve as model systems not only to conceive the bottomup synthesis of SWCNTs but also to elucidate the nature of the interaction of the nanotube host with guests, as well as other interesting properties. 13,14,15 Since the first synthesis of [n]CPPs (n=9, 12, and 18) in 2008, 16 the family of [n]CPPs was quickly expanded to include the n=5- 16, and 18 members of the series and diversified into other functionalized derivatives using various synthetic methods.…”

“…Irreversibility of[5]-and[6]CPP comes from the formation of new -bonds leading to new phases with aggregation and polymerization of the CPP molecules that start to occur around 6 GPa 21,22. The Raman spectra of[n]CPPs shown inFigures S14 and S18indicate that the spectra are irreversible after application of pressure for n=5, 6, and 8 while the spectra of[7]CPP,[9]CPP,[10]CPP, and[12]CPP are almost completely reversible in the pressure range studied. Since formation of new bonds are not predicted by the computer simulations for[n]CPPs with n>6 in the pressure range analyzed, it is natural to conclude that the structures of the remaining[n]CPPs are reversible and there are no permanent structural transformation resulting from the high pressure deformation.…”

Linear, Non-Conjugated Cyclic and Conjugated Cyclic Paraphenylene under Pressure

“…The unusual cyclic molecular symmetry of [n]CPPs offers a unique case of cyclic circulation of the π-electron density, or cyclic π-conjugation [13,18,19], which confers on them distinct optical and electronic properties governed by their increasing strain with decreasing n [20,21]. The versatility of these systems in terms of aromaticity, unique size-dependent supramolecular properties and encapsulation of guest molecules leads to promising applications in materials science [22,23,24,25,26,27].…”

Aggregation behavior and non‐covalent functionalization of borofullerenes B28, B38, and B40: A density functional theory investigation

“…For example, Yamago's group reported that C 60 can be selectively encapsulated by [10]CPP and detected the host‐guest interaction by 1 H‐NMR spectroscopy . A very recent report by González‐Veloso et al showed that [11]CPP could be capable of separating the fullerenes larger than C 76 from a mixture also containing C 60 and C 70 . The encapsulation by CPPs may not only lead to new functional materials, but also can be used for selective extraction of a given fullerene from mixture.…”