Gram-scale synthesis and crystal structures of [8]- and [10]CPP, and the solid-state structure of C60@[10]CPP

Solid-state structures of peapod bearings composed of finite single-wall carbon nanotube and fullerene molecules

“…Although severe disorders inherent to the dynamic bearing system hampered the analysis with ordinary X-ray beams, a synchrotron macromolecular crystallography beamline (BL41XU; SPring-8) (18) allowed us to solve the complex structure of the peapod at the atomic level. In the presence of chlorine atoms of CH 2 Cl 2 molecules in a single crystal of the chiral trigonal P3 2 space group at -173°C, we unequivocally assigned the absolute configuration of (12,8)- [4]CC 2,8 as (M)-helicity with a reliable Flack parameter of 0.13 (13). Note that this assignment finally confirmed the previous conclusion from the spectral and theoretical investigations (11).…”

“…We then conducted structural analysis using crystallographic methods. The crystal structure of vacant (12,8) 2,8 was obtained from a racemic mixture and revealed the tubular molecular structure through diffraction analysis with monochromated X-rays (BL-1A beamline; Photon Factory) (25). The average dihedral angle at the single-bond linkages was 18.48 ± 0.16°, which described the sp 2 -carbon atoms on a curved plane along the cylindrical axis ( Fig.…”

“…Although interesting physical phenomena of peapods are being discovered, especially in solid-state physics (2)(3)(4)(5), little fundamental and in-depth understanding of peapods has been accumulated at the molecular or atomic levels until quite recently. The first reports of structural chemistry related to peapods appeared through the studies of [10]cycloparaphenylene ([10]CPP) (6): Yamago and coworkers (7) first reported a moderate level of association (association constant K a ∼ 10 3 M in o-dichlorobenzene) with C 60 in the solution phase, and solid-state crystal structures were reported with C 60 and C 70 by Jasti and coworkers (8) and Yamago and coworkers (9). Although this moderate level of association in [10]CPP raised a question regarding the stability of peapods in general (5, 10), we recently showed that the association of belt-persistent tubular molecules, [4]cyclo-2,8-chrysenylenes ([4]CC 2,8 ) (11-13), with C 60 was much higher and recorded a 10 6 -and 10 9 -fold higher association constant in the same medium (K a ∼ 10 9 M) and in benzene (K a ∼ 10 12 M), respectively ( Fig.…”

Intra‐ and Intermolecular Dispersion Interactions in [n]Cycloparaphenylenes: Do They Influence Their Structural and Electronic Properties?

“…The crystal packing of these molecules was recently resolved [21], leading to the discovery of a (somewhat unexpected) structural change, passing from a solid-state herringbone packing in the set of [8 − 12]CPP molecules to a linear alignment of [6]CPP molecules forming a discontinuous, nanotubelike, structure. This supramolecular organization might drive, for instance, a consistent bottom-up synthesis of a (6, 6)SWNT.…”

“…As a matter of example, we summarize next some interesting and highly challenging achievements (in the supramolecular scale) recently accomplished in the field: (i) the encapsulation of C 60 by [10]-cycloparaphenylene ( [10]CPP), forming a host-guest complex stabilized roughly by 40 kcal/mol in toluene [20] and with both molecules separated by a distance of 3.35Å, which equals the interlayer separation in graphite; actually, not all the [n]CPP nanohoops (n = 8 − 12) are able to encapsulate C 60 [21], but only [10]CPP, which might arise from the interplay between attractive and repulsive intraand inter-molecular interactions; (ii) the association of C 70 or the metallofullerene La@C 82 with [11]CPP was also recently studied [22,23], and shows how both molecules are labile enough to accommodate each other, with [11]CPP adopting an ellipsoidal shape in the former case; (iii) the chirality in SWNTs might be induced by appropriately substituted cycloparaphenylenenaphthalenes [24] or cycloparaphenylene-naphthylenes [25] compounds, constituting thus the first step towards the controlled synthesis of chiroptical SWNTs, which might create a diversity of forms and release the strain energy of unsubstituted cycloparaphenylenes; and (iv) the dimerization of [n]CPP nanohoops, thanks to covalently-linked structures at only one specific position along the macrocycle, which might pave the way towards increasingly longer supramolecular architectures with customized nanochannels [26].…”