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1.
Sara Gil-Guerrero Prof. Manuel Melle-Franco Prof. Ángeles Peña-Gallego Prof. Marcos Mandado 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(68):16138-16143
The Clar Goblet, the first radical bowtie nanographene proposed by Erich Clar nearly 50 years ago, was recently synthesized. Bowtie nanographenes present quasi-degenerate magnetic ground states, which make them so elusive as unique. A thorough analysis is presented of the spin-state energetics of Clar Goblet and bowtie nanographenes by a battery of existing and novel ab initio procedures ranging from density functional theory to complete active space Hamiltonians. With this, it was proven that π radicals of bowtie nanographenes sit on BP (Benzo[cd]Pyrene) moieties driven by their local aromaticity, a purely chemical concept, which confers global stability to the whole structure. Besides, a novel Pauli energy densities analysis provided a visual intuitive explanation for this preference. These findings allow envisioning that analogous bowtie nanographenes with arbitrary polyradical character are not only feasible at the molecular scale but will share Clar Goblet's peculiar properties. 相似文献
2.
César Ruiz-Zambrana Rajeev K. Dubey Macarena Poyatos Prof. Aurelio Mateo-Alonso Prof. Eduardo Peris 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(44):e202201384
A series of rhodium and iridium complexes with a N-heterocyclic carbene (NHC) ligand decorated with a perylene-diimide-pyrene moiety are described. Electrochemical studies reveal that the complexes can undergo two successive one-electron reduction events, associated to the reduction of the PDI moiety attached to the NHC ligand. The reduction of the ligand produces a significant increase on its electron-donating character, as observed from the infrared spectroelectrochemical studies. The rhodium complex was tested in the [3+2] cycloaddition of diphenylcyclopropenone and methylphenylacetylene, where it displayed a redox-switchable behavior. The neutral complex showed moderate activity, which was suppressed when the catalyst was reduced. 相似文献
3.
Stephan Schaumüller Doris Cristurean Stephan Haudum George S. Pappas Markus Himmelsbach Matthias Bechmann Oliver Brüggemann Ian Teasdale 《Journal of polymer science. Part A, Polymer chemistry》2021,59(24):3161-3166
We report a facile post-polymerization modification route to functionalized aromatic polyimides via Diels-Alder cycloaddition. Aromatic polyimides are important, versatile high-performance polymers; however, their structural diversity is restricted by the requirements of the step-growth polymerization. We prepared polyimides with alkynes in their main-chain as macromolecular dienophiles and quantitatively grafted tetraphenylcyclopentadienone based dienes. The resulting solution-processable, wholly aromatic polyimides show a considerable increase in surface area due to the induced conformational changes and bulky, rigid, and contorted molecular structures. The orthogonality of the reaction is exploited to insert functional groups, namely bromine and sulfonates, along the polymer backbone. In a further extension, the phenylene segments undergo cyclodehydrogenation to form nanographene segments within the polymer chains. The Diels-Alder cycloaddition onto polyimides is therefore demonstrated to be an effective, widely applicable route to tunable high-performance polymers with value-added functionality and thus considerable potential in a wide range of advanced materials. 相似文献
4.
Sulfur‐Annulated Hexa‐peri‐hexabenzocoronene Decorated with Phenylthio Groups at the Periphery 下载免费PDF全文
Dr. Yuan‐Zhi Tan Dr. Silvio Osella Yi Liu Bo Yang Prof. Dr. David Beljonne Prof. Dr. Xinliang Feng Prof. Dr. Klaus Müllen 《Angewandte Chemie (International ed. in English)》2015,54(10):2927-2931
The chemical nature of the edge periphery essentially determines the physical properties of graphene. As a molecular‐level model system, large polycyclic aromatic hydrocarbons, that is, so‐called nanographenes, can be chemically modified through either edge functionalization or doping with heteroatoms. Although the synthetic methods for edge substitution are well‐developed, incorporation with heteroatoms by the bay annulation of large PAHs remains an enormous challenge. In this study, we present a feasible peripheral sulfur annulation of hexa‐peri‐hexabenzocoronene (HBC) by thiolation of perchlorinated HBC. The tri‐sulfur‐annulated HBC and di‐sulfur‐annulated HBC decorated with phenylthio groups were obtained and characterized by X‐ray diffraction, revealing their distinct sulfur‐annulated peripheral structure. Associated with theoretical calculations, we propose that the regioselective sulfur annulation results from the minimization of strain in the aromatic backbone. We further demonstrate the structure‐correlated property modulation by sulfur annulation, manifested by a decrease in band gap and tunable redox activity. 相似文献
5.
Magneto-electronic properties of asymmetric bilayer nanographene ribbons are enriched by geometric structures, interlayer atomic interactions, magnetic quantization and finite-size confinement. There are drastic changes on the band symmetry, the degeneracy of the partial flat bands, the number of band-edge states, the energy dispersion, the carrier density, and the spatial symmetry of the wave function. Quasi-Landau levels might be converted into oscillating bands where extra band-edge states are created. When the upper ribbon is located at the ribbon centre, the Landau wave functions are completely destroyed. Meanwhile, a charge transfer between different layers or different sublattices in the same layer occurs. Furthermore, the density of states, reflecting the band structure, is also severely altered in terms of the number, structure, energy, and height of the prominent peaks. 相似文献
6.
Dr. Paul J. Evans Dr. Jiangkun Ouyang Dr. Ludovic Favereau Dr. Jeanne Crassous Dr. Israel Fernández Dr. Josefina Perles Prof. Dr. Nazario Martín 《Angewandte Chemie (International ed. in English)》2018,57(23):6774-6779
A rigid, inherently chiral bilayer nanographene has been synthesized as both the racemate and enantioenriched M isomer (with 93 % ee) in three steps from established helicenes. This folded nanographene is composed of two hexa‐peri‐hexabenzocoronene layers fused to a [10]helicene, with an interlayer distance of 3.6 Å as determined by X‐ray crystallography. The rigidity of the helicene linker forces the layers to adopt a nearly aligned AA‐stacked conformation, rarely observed in few‐layer graphene. By combining the advantages of nanographenes and helicenes, we have constructed a bilayer system of 30 fused benzene rings that is also chiral, rigid, and remains soluble in common organic solvents. We present this as a molecular model system of bilayer graphene, with properties of interest in a variety of potential applications. 相似文献
7.
Computational studies have often been carried out on hydrogen-terminated nanographenes (NGs). These structures are, however, far from those deduced from experimental observations, which have suggested armchair edges with two carboxy groups on the edges as dominant. We conducted computational studies on NGs consisting of C42, C60, C78, C96, C142, and C174 carbon atoms with hydrogen, carboxy, and N-methyl imide-terminated armchair edges. DFT calculations inform distorted basal planes and similar HOMO-LUMO gaps, indicating that the edge oxidation and functionalization do not very influence the electronic structure. Comparison of observed UV-vis spectra of carboxy- and N-octadecyl chain terminated NGs with calculated spectra of model NGs informs the contribution of π-π* transitions on the basal plane to the absorptions in the visible region. A dimeric structure of NG and octadecyl-installed NG demonstrate that both the distorted basal planes and the steric contacts among the functional groups widen the surface-to-surface distance thereby allowing the invasion of solvent molecules between the surfaces. This picture is consistent with the improved solubility of edge-modified NGs. 相似文献
8.
Dominik Lorbach Dr. Ashok Keerthi Dr. Teresa Marina Figueira‐Duarte Prof. Dr. Martin Baumgarten Dr. Manfred Wagner Prof. Dr. Klaus Müllen 《Angewandte Chemie (International ed. in English)》2016,55(1):418-421
First synthesis of the macrocycle cyclohexa(1,3‐pyrenylene) is achieved in six steps starting with pyrene, leading to a non‐aggregating highly twisted blue‐light‐emitting material. The cyclodehydrogenation of the macrocycle offers a promising synthesis route to holey‐nanographene. 相似文献
9.
Giacomo Biagiotti Ilaria Perini Barbara Richichi Stefano Cicchi 《Molecules (Basel, Switzerland)》2021,26(20)
The success of the rational bottom-up approach to nanostructured carbon materials and the discovery of the importance of their doping with heteroatoms puts under the spotlight all synthetic organic approaches to polycyclic aromatic hydrocarbons. The construction of atomically precise heteroatom doped nanographenes has evidenced the importance of controlling its geometry and the position of the doping heteroatoms, since these parameters influence their chemical–physical properties and their applications. The growing interest towards this research topic is testified by the large number of works published in this area, which have transformed a once “fundamental research” into applied research at the cutting edge of technology. This review analyzes the most recent synthetic approaches to this class of compounds. 相似文献
10.
Sai Ho Pun Chi Kit Chan Dr. Jiye Luo Prof. Zhifeng Liu Prof. Qian Miao 《Angewandte Chemie (International ed. in English)》2018,57(6):1581-1586
This study presents a new type of negatively curved nanographene (C86H32) that contains an unprecedented pattern of heptagons. A tert‐butylated derivative of C86H32 was successfully synthesized using tetrabenzodipleiadiene as a key building block. This synthesis involved a ring expansion reaction as a key step to form the seven‐membered rings in the framework of tetrabenzodipleiadiene. The single‐crystal structure reveals a saddle‐shaped molecule with a highly bent naphthalene moiety at the center of the polycyclic backbone. As found from the DFT calculations, this aromatic saddle is flexible at room temperature and has a saddle‐shaped geometry as the dominant conformation. The DFT calculations along with experimental results show that the attachment of t‐butyl groups to the central tetrabenzodipleiadiene moiety of nanographene C86H32 can stabilize the saddle conformation and make this nanographene less flexible. 相似文献