Corannulene Polysulfides: Molecular Bowls with Multiple Arms and Flaps

Abstract

Nucleophilic aromatic substitution of all the chlorine atoms in 1,3,5,7,9-pentachlorocorannulene and in decachlorocorannulene by sodium alkanethiolates gives 1,3,5,7,9-pentakis(1-alkylthio)corannulenes, C 20 H 5 (SR) 5 , and decakis(1-alkylthio)corannulenes, C 20 (SR) 10 , respectively, with arms of varying lengths attached around the perimeter (R = n-propyl, n-hexyl, and ndodecyl). The corresponding reaction of decachlorocorannulene with ortho-C 6 H 4 (SNa) 2 gives pentakis(1,4-benzodithiino)corannulene, a molecular bowl with 6 Å flaps on all five sides. Such compounds represent attractive candidates for the formation of discotic liquid crystals and/or supramolecular complexes with fullerenes and other convex guests.Our discovery that the chlorination of corannulene (1) with I-Cl at room temperature gives pentachlorocorannulene with surprisingly high selectivity for the 1,3,5,7,9-isomer 2 1 opened the door to a new family of molecular bowls that bear substituents around the entire perimeter ( Figure 1). 1-3 Figure 1Corannulene (C 20 H 10 ) and several 1,3,5,7,9-pentakis-X derivatives Within this new family of compounds, the pentakis(SAr) derivatives 3 and 4 were found to be well-suited as hosts for the complexation of C 60 (K assoc = 10 2 -10 3 M -1 ). 3 The choice of aryl groups in these fullerene hosts was strongly influenced by the fact that C 60 exhibits good solubility in both anisole and methylnaphthalene, 4 and it is tempting to envision the arms of 3 and 4 embracing the C 60 in these complexes (Figure 2). This view is reinforced by the failure of unsubstituted corannulene (1) to show any evidence for binding to C 60 . 5Notwithstanding this appealing picture, the question remains whether or not 'intramolecular solvation' by the five tethered arenes represents the primary factor responsible for the superior binding ability of the pentakis(SAr) derivatives 3 and 4. The five sulfur atoms attached around the perimeter of the geodesic polyarene core in 3 and 4 must certainly render their concave surfaces more electron rich and more polarizable than the interior surface of the parent corannulene, and that could be the dominant factor. Figure 2 Hypothetical structure for the 1:1 complex C 60 ·3, with the five arms of 3 embracing the C 60To probe this issue, we have synthesized the 1,3,5,7,9-pentakis(S-CH 2 CH 2 CH 3 ) derivative 5, which lacks electron-rich p-systems on the arms but retains the geodesic polyarene core and the five attached sulfur atoms. As in our syntheses of 3 and 4, 3 the conversion of 2 to 5 could be effected under quite mild conditions. Thus, stirring 1,3,5,7,9-pentachlorocorannulene (2) with sodium 1-propanethiolate in 1,3-dimethylimidazolidin-2-one (dimethylethanourea = DMEU) at room temperature for 3 days gave 1,3,5,7,9-pentakis(1-propylthio)corannulene (5) in 38% yield, after purification. In the same manner, a 1,3,5,7,9-pentakis(1-alkylthio)corannulene with much longer arms 6 was also prepared from 2. 6 Starting from decachlorocorannulene (7), 7 the same reaction was used to make a fami...

From Induced-Fit Assemblies to Ternary Inclusion Complexes with Fullerenes in Corannulene-Based Molecular Tweezers

“…It is known that the presence of heteroatoms perturbs the electronic properties of the whole carbon/hydrogen system in terms of electrostatics and frontier orbitals energy levels. , In fact, corannulene chalcogenides, especially sulfur-derived corannulene compounds, − are among the most studied given the possibility of fine-tuning their properties depending on the number of substituents, the location of the heteroatom and its oxidation state. Scott and co-workers pioneered the host–guest chemistry of sulfur-derived corannulenes with fullerenes − obtaining moderate binding affinities, but overall outstanding considering there was only one corannulene core instead of a tweezer-like arrangement. According to their results, they concluded that the relative electron-rich orthophenylene substituents definitely contributed to the association enhancement, especially for their fly trap host, albeit a possible increased fullerene surface coverage could have had a higher impact through attractive dispersion forces.…”

Amphiphilic Corannulene Derivatives: Synthetic Access and Development of a Structure/Property Relationship in Thermoresponsive Buckybowl Amphiphiles

“…Scott and co-workers have employed a combination of the two motifs to design hosts of fullerene C 60 . 47,48 The optoelectronic properties of the persulfurated corannulene derivatives and 10-fold sulfuration of the corannulene nucleus are described by Baldridge and Siegel. 49,50 In the present context, a single substitution of the corannulene nucleus with an ethylene glycol-based side chain was considered as the simplest amphiphilic structure with which the investigations into the aforementioned questions could begin.…”

“…This powerful nucleophile can then be used for a substitution reaction with halocorannulene to establish a thio–ether linkage between the hydrophobic core and the hydrophilic side chain. 47,49,50 In this way, the simplest amphiphilic structure 2 was prepared and isolated in an 80% yield. After achieving synthesis of 2 , an increase in the polar ethylene glycol arm length was considered.…”

Corannulene Chalcogenides

“…Following the initial results, Scott extended his investigations by synthesizing a library of penta‐ and decasubstituted corannulenes ( 8 c – d and 10 – 11 ) decorated with alkyl/arylthio groups in 2004 (Scheme 2–3). [16] A year later, fullerene association studies of the two derivatives: pentakis(propylthio)corannulene 8 c and pentakis(1,2‐benzodithio)corannulene 11 were presented [17] . Due to the low solubility of these compounds in toluene, the association was investigated in a mixture of CS 2 and dimethylsulfoxide (DMSO).…”