The crystal and molecular structure of corannulene, C20H10

Abstract

Dibenzo [ghi, mno]fluoranthene, or corannulene, C20H10, is a highly strained hexacyclic hydrocarbon composed of five benzene rings fused into an annulus of fivefold symmetry. The compound crystallizes in space group P2t/c with Z=8 and cell dimensions a=13.260 (7), b= 11.859 (4), e= 16.520 (7) A,, fl= 102.69 (5) ° at 20°C, and a= 13.233 (15), b = 11.785 (15), c= 16.432 (15) A, fl= 102-55 (7) ° at -70°C. Data were obtained by densitometry of doubly integrated oscillation photographs at 20°C, and by diffractometer techniques at -70°C. The structure was solved by a Patterson search procedure. Refinement by block-diagonal least squares brought the final R value to 0.069 for 2013 data observed at 20°C and to 0.074 for 2137 data observed at -70°C. The molecules are cupped with an average dihedral angle of 20"4 ° between least-squares planes defined by the five-and six-membered rings. Averages of chemically equivalent bond distances (corrected for foreshortening due to molecular libration) from two crystallographically independent molecules and two independent sets of data are 1.413 (3) A, for the five bonds in the central ring, 1.391 (4) A, for the five 'spokes', 1.440 (2) A, for the ten peripheral bonds adjacent to the 'spokes', and 1.402 (5) A, for the five outermost peripheral bonds.1147

IR, Raman, and UV/Vis Spectra of Corannulene for Use in Possible Interstellar Identification

“…[5,6] They can also be compared with the recent theoretical results of Petrukhina et al [6] who calculated their values at several levels of theory. As their study did not include the use of the cc-pVTZ basis set, our results complement theirs.…”

“…The two most intense bands remain those at 661. 5 , respectively, which is a factor of two smaller than the widths observed in the pellet spectrum. This difference can be attributed to the different temperatures in the experiments, the cryogenic temperature giving rise to narrower bands relative to room temperature by reducing homogeneous and inhomogeneous broadening.…”

“…The three bands marked with asterisks in Figure 2 correspond, in the order of increasing wavenumbers, to a pair of out-ofplane vibrations of the carbon [a] Notation of ref. [5]. [b] Results of measurements at À100 8C from ref.…”

Infrared spectroscopy of ionized corannulene in the gas phase

“…The molecular structure resembles that of coronene (C 24 H 12 ), which consists of six aromatic rings symmetrically arranged around an inner sixmembered ring and which possesses D 6h symmetry. As shown by x-ray diffraction, 1 the bonds between the carbon atoms of the pentagonal ring and the peripheral benzenic rings are significantly out of the plane in corannulene. Therefore, the adopted curved geometry reduces the aromatic character of corannulene as compared to planar coronene.…”

A simple model for counter-rotating ring currents in [n]circulenes

“…Whilst 2 has a D 6h structure both in solution and in the solid state [9], 1 is bowl-shaped in the solid state [10] but has a time-averaged planar D 5h structure in solution (as established by temperature-dependent 1 H NMR) due to rapid bowl-to-bowl interconversion [11,12]. In contrast, 3 has a saddle-shaped structure of C 2 symmetry (3b) in the solid state [8] and a time-averaged planar structure of D 7h symmetry (3a) in solution (with one 1 H and three 13 C NMR resonances), which is not frozen out even at À90°C [13] (Fig.…”