Corannulene Molecular Rotor with Flexible Perfluorobenzyl Blades: Synthesis, Structure and Properties

Abstract

Two members of a new class of organic-acceptor perfluorobenzyl corannulenes were prepared by gas-phase and highly-selective solution-phase reactions at elevated temperatures. The peculiar single-crystal X-ray structure of C5-C20H5(CF2C6F5)5 revealed two high-energy conformers with drastically different bowl depths and orientations of perfluorobenzyl blades; the conformers are alternating in columnar packing arrangements and every pair is sandwiched by toluene molecules.

Corannulenes with Electron‐Withdrawing Substituents: Synthetic Approaches and Resulting Structural and Electronic Properties

“…Here, the electron‐withdrawing effect results in an anodic shift of 1.1 V, which is only slightly larger than that for compounds 19 a and 19 b . Fivefold perfluorobenzylated corannulene 9 reveals an irreversible reduction at about the same voltage . The highest shift in the reduction potential is observed for annulated derivative 10 with a value that is almost 1.25 V more positive.…”

“…For corannulenes with longer perfluoroalkyl chains, that is, 6 b , 15 b – d , one can only observe irreversible reductions at comparable potentials . Perfluorobenzylated derivative 8 could not be investigated . As expected, the introduction of a single fluorine substituent results only in a small electron‐withdrawing effect for 12 (≈0.1 V) …”

“…The crystal and molecular structures of several perfluoroalkyl and benzyl derivatives of corannulene with one to seven substituents have been determined by single‐crystal X‐ray diffraction. All of them have bowl depths between 0.54 and 0.87 Å . The bowl depth decreases with the number of substituents and is particularly small for cases in which two bowls are adjacent to each other on the convex side of the bowl.…”

“…Ar elated transformation with perfluorobenzyl iodide to yield (perfluorobenzyl)corannulene (8)i nt he liquid phase and 1,3,5,7,9-pentakis(perfluorobenzyl)corannulene (9)i nagasphase reactionh as been described (Scheme 4). [29] Further,i ti s possible to treat corannulene with a,w-perfluoroalkyl diiodides to obtain annulated corannulene derivatives 10 and 11 (Scheme5). [30] The main drawback of all of these reactions is the rather low selectivity and the obligatoryn eed for purification by HPLC methods.…”

Experimental and DFT Studies of the Electron‐Withdrawing Ability of Perfluoroalkyl (RF) Groups: Electron Affinities of PAH(RF)n Increase Significantly with Increasing RF Chain Length

“…(The use of CF 3 and longer-chain R F groups as substituents for hundreds of derivatives of C 60 ,C 70 ,a nd other fullerenes is the subject of ar ecent review). [22] Since that time we have prepared and studied R F derivatives of an umber of polycyclic aromatic hydrocarbons (PAHs), includingn aphthalene( NAPH), [23] anthracene (ANTH), [24] and CORA, [25][26][27] among others. [28][29][30][31] Here, we report experimental and/orD FT-predicted EAs of 13 homologous series of PAH(R F ) n compounds with one to six R F substituents.…”