Corannulene Amino Acid-Derived Water-Soluble Amphiphilic Buckybowls as Broad-Spectrum Membrane Targeting Antibacterial Agents

To date, the use of corannulene has been restricted in the area of material science, but its application in biomedical research has yet to be established due to its nonsolubility in an aqueous environment and synthetic infeasibility. Herein, we detail the development of a new family of highly curved π-conjugated corannulene-containing unnatural α-amino acid (CAA) derivatives to overcome this challenge. These CAAs have been extended as novel constituents for the synthesis of corannulene-containing water-soluble cationic peptides (CCPs), which display inhibitory activity against broad-spectrum pathogenic bacteria along with drug-resistant bacteria via a membrane-damaging mechanism. Importantly, several of the synthesized peptides were found to be appreciably nonhemolytic against hRBCs and noncytotoxic against mammalian 3T3 cells. In vivo efficacy studies of the potent and least cytotoxic peptide 6a demonstrated clearance of bacteria from the spleen, liver, lung, and blood of mice infected with S. aureus ATCC 25923.

Gold-Catalyzed Precise Bromination of Polystyrene

Modification of commodity aromatic polymers is highly desirable for accessing materials with new properties. The long-standing challenge for such approaches lies in the development of catalytic methods that can functionalize the aromatic polymers with high precision while preserving the molecular weight and distribution of the starting polymers without any alteration. Herein, we report a highly efficient AuCl₃-catalyzed site-selective aromatic C-H halogenation of polystyrene. The most important feature of this method is that the degree of halogenation can be precisely controlled by simply changing the loading of the halogenating agent, thus allowing the tuning of functional group density in an accurate and predictable manner. Various functional groups, including NH₂ and Bpin, can be installed through effective derivatization of the resultant brominated polystyrene, thus making the method a valuable strategy for the synthesis of value-added materials with tailored properties.

Mono- and sym-pentahalogenated corannulenes: reaction optimization & purification by in process product analysis

A robust, mild & inexpensive synthetic route to mono-halogenated corannulene and a robust method for purifying and analyzing sym-pentachlorocorannulene from the ICl halogenation of corannulene is reported.

Introducing Distinct Structural and Optical Properties into Organotin Sulfide Clusters by the Attachment of Perylenyl and Corannulenyl Groups

We report the introduction of distinct optical properties into organotin sulfide clusters by the attachment of extended polycyclic aromatic organic molecules. This was realized by the reactions of [(R^NSn)₄S₆] (R^N = CMe₂CH₂CMeNNH₂) with 3-perylenecarbaldehyde and corannulenecarbaldehyde, respectively. The reaction with the first reactant leads to the formation of two products [(R^perylSn)₃S₄][SnCl₃] [1a; R^peryl = CMe₂CH₂CMeNNCH(C₂₀H₁₁)] and [(R^perylSn)₃S₄Cl] (1b). Structural differences between these two compounds are reflected in their different optical absorption and luminescence behavior, yet in both cases, the main emission is red-shifted relative to 3-perylenecarbaldehyde. The second organic molecule affords the compound [(R^corSn)₄Sn₂S₁₀] [2; R^cor = CMe₂CH₂CMeNNCH(C₂₀H₉)] with intriguing optical properties, including a broad emission with essentially no shift in λ_max compared to corannulenecarbaldehyde. All compounds were obtained as single crystals, and their structures were determined by means of single-crystal X-ray diffraction. The optical properties of the highly luminescent compounds were investigated by means of emission and time-resolved photoluminescence spectroscopy measurements.

Five-Fold Symmetric Pentaindolo- and Pentakis(benzoindolo)Corannulenes: Unique Structural Dynamics Derived from the Combination of Helical and Bowl Inversions

Peripherally π-extended corannulenes bearing quintuple azahelicene units, 10 and 11, were prepared and their dynamic behaviors were studied experimentally and theoretically. The fused corannulenes were synthesized from sym-pentabromocorannulene in three steps. X-Ray diffraction analysis for 10 displayed a conformer possessing a P(M) bowl chirality and a PPMPM (PMPMM) helical chirality, which was found to be the most stable conformer(s). Variable-temperature NMR measurements of 10 and 11 revealed that their structural isomers can be interconvertible in solution, depending on the steric congestion around the helical scaffolds. Automated search for conformers in the equilibrium and transition states by Artificial Force Induced Reaction (AFIR) method revealed their interconversion networks, including bowl-inversion and helical-inversion. This analysis indicated that the co-existing corannulene and azahelicene moieties influence the conformational dynamics, which leads to mitigation of the activation energy barriers for isomerization.

Thiophene fused indenocorannulenes: synthesis, variable emission, and exceptional chiral configurational stability

Graph theory and isosteric replacement leads to the design and synthesis of (chiral) thiophene-fused indenocorannulenes with exceptional configurational stability and possible use as chiral catalysts, chiroptical materials, and sensors.

Geodesic-Planar Conjugates: Substituted Buckybowls-Synthesis, Photoluminescence and Electrochemistry

C-C cross coupling products of bowl-shaped as-indaceno[3,2,1,8,7,6-pqrstuv]picene (Idpc) and different planar arenes and ethynyl-arenes were synthesized. Photoluminescence as well as electrochemical properties of all products were investigated and complemented by time-dependent quantum chemical calculations. UV/Vis spectroelectrochemistry investigations of the directly linked (Idpc)2 indicated the absence of any intramolecular charge-transfer transition of intermittently formed (Idpc)2 .- . All coupling products showed fluorescence. Ferrocene-1-yl-Idpc was structurally characterized by X-ray diffraction and is a rare example of a ferrocene-containing buckybowl exhibiting luminescence.

Octapodal Corannulene Porphyrin-Based Assemblies: Allosteric Behavior in Fullerene Hosting

An octapodal corannulene-based supramolecular system has been prepared by introducing eight corannulene moieties in a porphyrin scaffold. Despite the potential of this double picket fence porphyrin for double-tweezer behavior, NMR titrations show exclusive formation of 1:1 adducts. The system exhibits very strong affinity for C₆₀ and C₇₀ (K₁ = (2.71 ± 0.08) × 10⁴ and (2.13 ± 0.1) × 10⁵ M^-1, respectively), presenting selectivity for the latter. Density functional theory (DFT) calculations indicate that, in addition to the four corannulene units, the relatively flexible porphyrin tether actively participates in the recognition process, resulting in a strong synergistic effect. This leads to a very strong interaction with C₆₀, which in turn also induces a large structural change on the other face (second potential binding site), leading to a negative allosteric effect. We also introduced Zn²⁺ in the porphyrin core in an attempt to modulate its flexibility. The resulting metalloporphyrin also displayed single-tweezer behavior, albeit with slightly smaller binding constants for C₆₀ and C₇₀, suggesting that the effect of the coordination of fullerene to one face of our supramolecular platform was still transmitted to the other face, leading to the deactivation of the second potential binding site.

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

Corannulene is a multifaceted polyaromatic compound. It has many interesting properties; for example, it has a bowl-shaped molecular structure that, in addition, undergoes a dynamic inversion process. It has attracted much attention within the last decades. This is not only due to its structural properties but also its electronic properties and its various potential applications to materials chemistry. Here, synthetic approaches towards corannulene derivatives with electron-withdrawing substituents are summarized. This includes both selective and unselective methods. Further, the electrochemical properties, that is, the reduction potentials, are analyzed and compared. As a main conclusion, one can state that the electron affinity depends roughly linearly on the number of substituents. Finally, the structural behavior of the substituted buckybowls in the solid state is highlighted. This also allows a general statement about the influence of the electronic and steric nature of substituents on the molecular structures and the solid-state packing of the corannulene derivatives.

A chelating bis(aminophenol) ligand bridged by a 1,1′-ferrocene-bis(para-phenylene) linker

The 1,1′-ferrocene-bis(p-phenylene) group serves as a structural linker connecting two iminosemiquinones to palladium without significant electronic interactions between the ferrocene and the palladium complex.

Buckybowls: Corannulene and Its Derivatives

Corannulene, a kind of bowl like polycyclic aromatic hydrocarbon (PAH), whose molecule is composed of a central pentagon and five closely adjacent hexagons on the pentagon's five sides, has received great scientific interest among research groups. In this review, the syntheses, characteristic molecule structure and properties of corannulene are clarified, as well as its derivatives with different substituted groups, fused derivatives, metal complex, and derivatives for host guest chemistry. On the basis of reviewing the applications and properties of corannulene together with its derivatives, the potential applications in hydrogen storage and lithium storage were highlighted and prospected.

The effect of heterocyclic π bridges on second order nonlinear optical properties of compounds formed between ferrocenyl and corannulenyl

Among D–π–A type compounds, when imidazole acts as a π bridge (endo/exo-3), the β_tot values are almost 2 times as large as when the phenyl acts as a π bridge (endo/exo-2).

Iridium-catalyzed reductive carbon-carbon bond cleavage reaction on a curved pyridylcorannulene skeleton

The cleavage of CC bonds in π-conjugated systems is an important method for controlling their shape and coplanarity. An efficient way for the cleavage of an aromatic CC bond in a typical buckybowl corannulene skeleton is reported. The reaction of 2-pyridylcorannulene with a catalytic amount of IrCl3 ⋅n H2 O in ethylene glycol at 250 °C resulted in a structural transformation from the curved corannulene skeleton to a strain-free flat benzo[ghi]fluoranthene skeleton through a site-selective CC cleavage reaction. This cleavage reaction was found to be driven by both the coordination of the 2-pyridyl substituent to iridium and the relief of strain in the curved corannulene skeleton. This finding should facilitate the design of carbon nanomaterials based on CC bond cleavage reactions.

Fluorinated and trifluoromethylated corannulenes

The syntheses and properties of corannulenes carrying electron-withdrawing groups (F, CF3 , C6 F5 ) are reported. Direct fluorination of corannulene (C20 H10 ) was carried out with xenon difluoride, and the crystal structure of the product was confirmed by the X-ray analysis. Novel trifluoromethylated corannulenes, including the versatile 4,9-dibromo-1,2-bis(trifluoromethyl)corannulene, were obtained by various established ring-closing reactions. Besides the use of hexafluorobutyne for the construction of fluoranthenes by Diels-Alder reaction as precursor molecules to form 1,2-disubstituted corannulenes, bis(pentafluorophenyl)acetylene was employed as dienophile. The molecular structure and crystal packing of a trifluoromethylated corannulene was determined by single-crystal X-ray analysis and compared with those known brominated and trifluoromethylated corannulenes. The general electron-acceptor properties of corannulenes bearing substituents introduced in particular positions by liquid-phase synthesis are discussed together with published computational results.