Weighting non-covalent forces in the molecular recognition of C60. Relevance of concave–convex complementarity

The relative contributions of several weak intermolecular forces to the overall stability of the complexes formed between structurally related receptors and [60]fullerene are compared, revealing a discernible contribution from concave–convex complementarity.Viruela Martin, Pedro Manuel, [email protected] ; Viruela Martin, Rafael, [email protected] ; Orti Guillen, Enrique, [email protected]

25,26-Bis(propan-2-yl­idene)hepta­cyclo[20.2.1.110,13.02,21.03,8.09,14.015,20]hexa­cosa-2(21),3,5,7,9(14),11,15,17,19,23-deca­ene

In the title compound, C32H28, the central cyclo­octa­tetra­ene ring has a boat conformation, and the mol­ecule is saddle shaped. The seat is defined by the mean plane of the four-atom attachment points (r.m.s. deviation = 0.014 Å) of the two bicyclo­heptenyl substituents. These substituents comprise the pommel and cantle, with each mean plane defined by four atoms proximate to the seat (r.m.s. deviations = 0.002 and 0.004 Å). Relative to the seat, the pommel and cantle bend up 31.16 (4) and 29.40 (5)°, while the benzo units (flaps, r.m.s. deviations = 0.006 and 0.009 Å) bend down 36.75 (4) and 38.46 (4)°. The mean planes of the dimethyl­ethyl­idene units are almost perpendicular to the saddle seat, making dihedral angles 86.89 (4) and 88.01 (4)°

Search for corannulene (C20H10) in the Red Rectangle

Polycyclic Aromatic Hydrocarbons (PAHs) are widely accepted as the carriers of the Aromatic Infrared Bands (AIBs), but an unambiguous identification of any specific interstellar PAH is still missing. For polar PAHs, pure rotational transitions can be used as fingerprints for identification. Combining dedicated experiments, detailed simulations and observations, we explored the mm domain to search for specific rotational transitions of corannulene (C20H10). We performed high-resolution spectroscopic measurements and a simulation of the emission spectrum of UV-excited C20H10 in the environment of the Red Rectangle, calculating its synthetic rotational spectrum. Based on these results, we conducted a first observational campaign at the IRAM 30m telescope towards this source to search for several high-J rotational transitions of (C20H10). The laboratory detection of the J = 112 <- 111 transition of corannulene showed that no centrifugal splitting is present up to this line. Observations with the IRAM 30m telescope towards the Red Rectangle do not show any corannulene emission at any of the observed frequencies, down to a rms noise level of Tmb = 8 mK for the J =135 -> 134 transition at 137.615 GHz. Comparing the noise level with the synthetic spectrum, we are able to estimate an upper limit to the fraction of carbon locked in corannulene of about 1.0x10(-5) relative to the total abundance of carbon in PAHs. The sensitivity achieved shows that radio spectroscopy can be a powerful tool to search for polar PAHs. We compare this upper limit with models for the PAH size distribution, emphasising that small PAHs are much less abundant than predicted. We show that this cannot be explained by destruction but is more likely related to the chemistry of their formation in the environment of the Red Rectangle.Comment: 8 pages, 7 figures, 2 tables, accepted for publication in MNRA

η⁶-Corannulene Buckybowl Complexes of Iridium, Including Ring-to-Ring Migration

Corannulene (C20H10, 1), a curved-surface fragment of buckminsterfullerene (C60), forms an η6-coordinated complex with Cp*Ir2+. The analogous 1,2,5,6-tetramethylcorannulene (2) complex, Cp*Ir(η6-2)2+, initially forms three isomers, but migration of the Cp*Ir2+ unit from a nonmethylated to a methylated ring gives two isomers in the final product

A Double Concave Hydrocarbon Buckycatcher

Double Diels−Alder addition of isocorannulenofuran to dibenzocyclooctadiyne followed by deoxygenation produces a molecular tweezers C60H28 with two corannulene pincers and a tetrabenzocyclooctatetraene tether. X-ray crystal structure determination of its inclusion complex with buckminsterfullerene C60 provides experimental evidence for the importance of attractive concave−convex π−π interactions in the supramolecular chemistry of fullerenes with buckybowls. An association constant of 8600 ± 500 M-1 was estimated for the complex formation by NMR titration experiment in toluene-d8

A Double Concave Hydrocarbon Buckycatcher

Double Diels−Alder addition of isocorannulenofuran to dibenzocyclooctadiyne followed by deoxygenation produces a molecular tweezers C60H28 with two corannulene pincers and a tetrabenzocyclooctatetraene tether. X-ray crystal structure determination of its inclusion complex with buckminsterfullerene C60 provides experimental evidence for the importance of attractive concave−convex π−π interactions in the supramolecular chemistry of fullerenes with buckybowls. An association constant of 8600 ± 500 M-1 was estimated for the complex formation by NMR titration experiment in toluene-d8

A Double Concave Hydrocarbon Buckycatcher

Double Diels−Alder addition of isocorannulenofuran to dibenzocyclooctadiyne followed by deoxygenation produces a molecular tweezers C60H28 with two corannulene pincers and a tetrabenzocyclooctatetraene tether. X-ray crystal structure determination of its inclusion complex with buckminsterfullerene C60 provides experimental evidence for the importance of attractive concave−convex π−π interactions in the supramolecular chemistry of fullerenes with buckybowls. An association constant of 8600 ± 500 M-1 was estimated for the complex formation by NMR titration experiment in toluene-d8