146885-81-6

Synthesis of corannulene and alkyl corannulene derivatives has been accomplished using solution-phase chemistry. The key step in the synthesis is the coupling of benzylic bromides of 1,6,7,10-tetraalkylfluoranthene derivatives by low-valent titanium to construct the corannulene nucleus. The use of low-valent titanium represents a viable alternative to flash vacuum pyrolysis methods previously developed. Corannulene (1), methylcorannulene (8), three different dimethylcorannulenes (2, 3, 5), two different tetramethylcorannulenes (4, 6), acecorannulylene (7), C5h symmetric pentamethylcorannulene (9), and decamethylcorannulene (10) have been prepared using low-valent titanium carbon-carbon coupling chemistry and halogen for alkyl exchange chemistry mediated by trimethylaluminum and catalytic nickel salts.

We report the first example of a donor–acceptor corannulene-containing hybrid material with rapid ligand-to-ligand energy transfer (ET). Additionally, we provide the first time-resolved photoluminescence (PL) data for any corannulene-based compounds in the solid state. Comprehensive analysis of PL data in combination with theoretical calculations of donor–acceptor exciton coupling was employed to estimate ET rate and efficiency in the prepared material. The ligand-to-ligand ET rate calculated using two models is comparable with that observed in fullerene-containing materials, which are generally considered for molecular electronics development. Thus, the presented studies not only demonstrate the possibility of merging the intrinsic properties of π-bowls, specifically corannulene derivatives, with the versatility of crystalline hybrid scaffolds, but could also foreshadow the engineering of a novel class of hierarchical corannulene-based hybrid materials for optoelectronic devices.

The solution-phase synthesis of corannulene has been modified and it is now possible to prepare multi gram quantities of corannulene more efficiently, with considerably less toxic reagents. Cross-coupling of bromocorannulene with TMS-acetylene and phenylacetylene affords novel ethynyl-containing corannulene derivatives. Deprotection of TMS-ethynyl corannulene affords the naked alkyne, which can be cross-coupled with pentafluoroiodobenzene and bromocorannulene to afford the appropriate alkyne derivatives. The photophysical properties of this new and novel family of alkyne-containing corannulene derivatives has been evaluated and all of the new derivatives exhibit low to moderate quantum efficiencies.

The structure and synthesis of the overcrowded polynuclear aromatic 1,6,7,10-tetramethylfluoranthene, 1, is presented.The structures of 1 and 11 have been determined by X-ray diffraction to be twisted into conformations of approximately C2 symmetry due to the buttressing of the flanking methyl groups.Semi-empirical calculations (AM1) on 1 find two minima, twist and fold; the twist is of lower energy.The energy for enantiomerization of 1 is set at below 7.0 kcal/mol by variable temperature NMR.Computations predict a likely path to account for the ribbon twist.

We report the first examples of purely organic donor–acceptor materials with integrated π-bowls (πBs) that combine not only crystallinity and high surface areas but also exhibit tunable electronic properties, resulting in a four-orders-of-magnitude conductivity enhancement in comparison with the parent framework. In addition to the first report of alkyne–azide cycloaddition utilized for corannulene immobilization in the solid state, we also probed the charge transfer rate within the Marcus theory as a function of mutual πB orientation for the first time, as well as shed light on the density of states near the Fermi edge. These studies could foreshadow new avenues for πB utilization for the development of optoelectronic devices or a route for highly efficient porous electrodes.

An efficient entry process for the synthesis of corannulene has been demonstrated on kilogram scale. Compared to the discovery and gram-scale syntheses, the amounts of solvents and reagents per gram of product were greatly reduced. Priority was given to implement the least toxic agents possible. Improvements in the purification of products obviated the need for column chromatography, alleviating four chromatographic operations. A new reduction method for the final step of the synthesis decreased reaction time from 6 to 0.5 days, and avoided the use of 100 equiv of zinc metal. The process now comprises nine steps, each of which runs smoothly at 100-L scale with a charging of 3-12 kg of educt. A total of 1.3 kg corannulene was isolated. This kilogram-scale process reduces material costs by over 2 orders of magnitude compared to that for the published gram-scale syntheses. Key opportunities in the process are identified for further improvements that should make synthesis on 100-kg scale feasible with a target price for 1 that is suitable for commercial production and engineering application.

Buckybowls: The adsorption of penta-tert-butylcorannulene, a molecule with fivefold symmetry, on Cu(111), a surface with threefold symmetry, is investigated by scanning tunneling microscopy complemented by structure calculations. The symmetry mismatch is

(Graph Presented) Four series of multiarmed chiral aryl ethers carrying two, three, five, or eight side-chains on a variety of aromatic core molecules (2-5) were prepared. The structure and conformation of 2 and 3 (in the solid state) were determined by the X-ray crystallographic analyses. While a pair of alternated (anti) conformers (i.e, up-down and down-up) were found in the crystal of 2, three side-arms in 3 were aligned in the same direction to give a C3-symmetric syn-conformation. Examinations by dispersion-corrected density functional (DFT-D) calculations revealed that two out of six anti- and two out of four syn-conformers of 2 are energetically most important. Two calculated structures of anti-conformers are in good agreement with those found in the solid state by X-ray analysis. Similarly, relevant conformations of syn-3, fully alternated 4, and C5-symmetric 5 were optimized at the DFT-D-B-LYP/TZVP level. The structure and conformation of the side-arms in 2-5 in solution were further studied by temperature dependent 1H NMR and UV-vis spectroscopy. In addition, comparative experimental and theoretical CD spectral studies were carried out in order to elucidate the contribution of the thermodynamically less-stable minor isomers in solution. The CD spectral changes observed for 2 and 3 at varying temperatures were quite different, while the parent chiral arene 1, as well as 4 and 5, only showed an increased intensity of the negative Cotton effect for the 1Lb band. The latter behavior is readily accounted for in terms of the conformational freezing of the chiral groups at low temperatures. The unusual CD spectral behavior observed for 2 and 3 was rationalized by the conformational alteration of the side-arms. Because of attractive van der Waals interactions between the aromatic units of the arms in nonpolar solvents, the syn-conformations become gradually more important for 2 at low temperatures, which eventually results in a weak positive Cotton effect for the 1Lb band. This was also supported by the SCS-MP2/TZVPP single-point energy calculations for the relevant conformers of 2. For 3, the contribution of the C3-symmetrical conformer becomes more important than the less-symmetrical isomers at low temperatures. The conformations of 2 and 3 in their excited states as well as in the oxidized states were also examined.