共查询到20条相似文献,搜索用时 15 毫秒
1.
Jie Su Mykola Telychko Shaotang Song Jiong Lu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(20):7730-7740
Triangulene and its higher homologues are a class of zigzag-edged triangular graphene molecules (ZTGMs) with high-spin ground states. These open-shell molecules are predicted to host ferromagnetically coupled edge states with net spin values scaling with molecular size and are therefore considered promising candidates for future molecular spintronics applications. Unfortunately, the synthesis of unsubstituted [n]triangulenes and the direct observation of their edge states have been a long-standing challenge due to a high reactivity towards oxygen. However, recent advances in precursor design enabled the on-surface synthesis and characterization of unsubstituted [3]-, [4]-, and [5]triangulene. In this Minireview, we will highlight key aspects of this rapidly developing field, ranging from the principles of precursor design to synthetic strategies and characterization of a homologous series of triangulene molecules synthesized on-surface. We will also discuss challenges and future directions. 相似文献
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Luis M. Mateo Qiang Sun Shi‐Xia Liu Jesse J. Bergkamp Kristjan Eimre Carlo A. Pignedoli Pascal Ruffieux Silvio Decurtins Giovanni Bottari Roman Fasel Tomas Torres 《Angewandte Chemie (International ed. in English)》2020,59(3):1334-1339
On‐surface synthesis offers a versatile approach to prepare novel carbon‐based nanostructures that cannot be obtained by conventional solution chemistry. Graphene nanoribbons (GNRs) have potential for a variety of applications. A key issue for their application in molecular electronics is in the fine‐tuning of their electronic properties through structural modifications, such as heteroatom doping or the incorporation of non‐benzenoid rings. In this context, the covalent fusion of GNRs and porphyrins (Pors) is a highly appealing strategy. Herein we present the selective on‐surface synthesis of a Por–GNR hybrid, which consists of two Pors connected by a short GNR segment. The atomically precise structure of the Por–GNR hybrid has been characterized by bond‐resolved scanning tunneling microscopy (STM) and noncontact atomic force microscopy (nc‐AFM). The electronic properties have been investigated by scanning tunneling spectroscopy (STS), in combination with DFT calculations, which reveals a low electronic gap of 0.4 eV. 相似文献
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Yubin Fu Huan Yang Yixuan Gao Li Huang Reinhard Berger Junzhi Liu Hongliang Lu Zhihai Cheng Shixuan Du Hong‐Jun Gao Xinliang Feng 《Angewandte Chemie (International ed. in English)》2020,59(23):8873-8879
We report the first bottom‐up synthesis of NBN‐doped zigzag‐edged GNRs (NBN‐ZGNR1 and NBN‐ZGNR2) through surface‐assisted polymerization and cyclodehydrogenation based on two U‐shaped molecular precursors with an NBN unit preinstalled at the zigzag edge. The resultant zigzag‐edge topologies of GNRs are elucidated by high‐resolution scanning tunneling microscopy (STM) in combination with noncontact atomic force microscopy (nc‐AFM). Scanning tunneling spectroscopy (STS) measurements and density functional theory (DFT) calculations reveal that the electronic structures of NBN‐ZGNR1 and NBN‐ZGNR2 are significantly different from those of their corresponding pristine fully‐carbon‐based ZGNRs. Additionally, DFT calculations predict that the electronic structures of NBN‐ZGNRs can be further tailored to be gapless and metallic through one‐electron oxidation of each NBN unit into the corresponding radical cations. This work reported herein provides a feasible strategy for the synthesis of GNRs with stable zigzag edges yet tunable electronic properties. 相似文献
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Hui Chen Lei Tao Dongfei Wang Zhuo‐Yan Wu Jun‐Long Zhang Song Gao Wende Xiao Shixuan Du Karl‐Heinz Ernst Hong‐Jun Gao 《Angewandte Chemie (International ed. in English)》2020,59(40):17413-17416
The thermally induced cyclodehydrofluorization of iron tetrakis(pentafluorophenyl)porphyrin proceeded highly stereoselectively to give a prochiral product on a gold surface in an ultrahigh vacuum, whereas dehydrocyclization of the respective iron tetrakisphenylporphyrin did not show such selectivity. Stereoselectivity was predominantly observed for closely packed layers, which is an indication of intermolecular cooperativity and steric constraints induced by adjacent species. Density functional theory identified intermolecular packing constraints as the origin of such selectivity during the reaction. Scanning tunneling microscopy revealed the formation of an enantiomerically pure two‐dimensional self‐assembly as a conglomerate of mirror domains. On‐surface two‐dimensional topochemistry, as reported herein, may open new routes for stereoselective synthesis. 相似文献
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The on‐surface coupling reactions of terminal alkynes catalyzed by exogenous cupric ions on chemically inert highly oriented pyrolytic graphite (HOPG) surface have been investigated by scanning tunnelling microscopy. In the presence of exogenous cupric ions, diyne‐linked nanostructures generated via homocoupling of terminal alkynes are the exclusive products, whereas no coupling reaction occurs for the terminal alkynes on the surface in the absence of the cupric ions, suggesting that exogenous cupric ions are efficient to catalyze the highly chemoselective on‐surface reaction of terminal alkynes. The HOPG surface displays a template effect to the growth and alignment of the products on the surface. As a result, 2D arrays of diyne‐linked zigzag polymers and 2D diyne‐linked porous polymers are fabricated from ditopic monomer 3,6‐diethynylcarbazole and tritopic monomer 1,3,5‐tris‐(4‐ethynylphenyl) benzene, respectively. This synthetic strategy combining the high selectivity of cupric ion catalyst as well as the template effect of on‐surface synthesis approach could be a general strategy to fabricate diyne‐linked nanostructures and nanomaterials on solid surfaces. 相似文献
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Rafal Zuzak Dr. Ruth Dorel Dr. Marek Kolmer Prof. Marek Szymonski Dr. Szymon Godlewski Prof. Antonio M. Echavarren 《Angewandte Chemie (International ed. in English)》2018,57(33):10500-10505
A unified approach to the synthesis of the series of higher acenes up to previously unreported undecacene has been developed through the on‐surface dehydrogenation of partially saturated precursors. These molecules could be converted into the parent acenes by both atomic manipulation with the tip of a scanning tunneling and atomic force microscope (STM/AFM) as well as by on‐surface annealing. The structure of the generated acenes has been visualized by high‐resolution non‐contact AFM imaging and the evolution of the transport gap with the increase of the number of fused benzene rings has been determined on the basis of scanning tunneling spectroscopy (STS) measurements. 相似文献
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Comparing Ullmann Coupling on Noble Metal Surfaces: On‐Surface Polymerization of 1,3,6,8‐Tetrabromopyrene on Cu(111) and Au(111) 下载免费PDF全文
Dr. Tuan Anh Pham Dr. Fei Song Dr. Manh‐Thuong Nguyen Dr. Zheshen Li Florian Studener Prof. Meike Stöhr 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5937-5944
The on‐surface polymerization of 1,3,6,8‐tetrabromopyrene (Br4Py) on Cu(111) and Au(111) surfaces under ultrahigh vacuum conditions was investigated by a combination of scanning tunneling microscopy (STM), X‐ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. Deposition of Br4Py on Cu(111) held at 300 K resulted in a spontaneous debromination reaction, generating the formation of a branched coordination polymer network stabilized by C?Cu?C bonds. After annealing at 473 K, the C?Cu?C bonds were converted to covalent C?C bonds, leading to the formation of a covalently linked molecular network of short oligomers. In contrast, highly ordered self‐assembled two‐dimensional (2D) patterns stabilized by both Br?Br halogen and Br?H hydrogen bonds were observed upon deposition of Br4Py on Au(111) held at 300 K. Subsequent annealing of the sample at 473 K led to a dissociation of the C?Br bonds and the formation of disordered metal‐coordinated molecular networks. Further annealing at 573 K resulted in the formation of covalently linked disordered networks. Importantly, we found that the chosen substrate not only plays an important role as catalyst for the Ullmann reaction, but also influences the formation of different types of intermolecular bonds and thus, determines the final polymer network morphology. DFT calculations further support our experimental findings obtained by STM and XPS and add complementary information on the reaction pathway of Br4Py on the different substrates. 相似文献
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Reactions of 5-(p-aminophenyl)-10,15,20-triphenyl porphyrin (1) with Ru3(CO)12 or M(OCOCH3)2 (M=Ni,Mn) afforded metalloporphyrins(4-6),respectively.6-Deoxy-6-io-do-β-cyclodextrin(2) and mono(6-O-trifluoromethanesulfonyl) permethylated β-cyclodextrin(3) reacted with complexes 4-6 to give β-cyclodextrin bonded metal porphyrins (7-9) and permethylated β-cyclodextrin bonded me-tal porphyrins (10-12) respectively.These new complexes were identified by MS,IR,UV-visible and ^1H NMR spectra,and elemental analysis. 相似文献
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Ana Snchez‐Grande Bruno delaTorre Jos Santos Borja Cirera Koen Lauwaet Taras Chutora Shayan Edalatmanesh Pingo Mutombo Johanna Rosen Radek Zboil Rodolfo Miranda Jonas Bjrk Pavel Jelínek Nazario Martín David cija 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(20):6631-6635
Engineering low‐band‐gap π‐conjugated polymers is a growing area in basic and applied research. The main synthetic challenge lies in the solubility of the starting materials, which precludes advancements in the field. Here, we report an on‐surface synthesis protocol to overcome such difficulties and produce poly(p‐anthracene ethynylene) molecular wires on Au(111). To this aim, a quinoid anthracene precursor with =CBr2 moieties is deposited and annealed to 400 K, resulting in anthracene‐based polymers. High‐resolution nc‐AFM measurements confirm the nature of the ethynylene‐bridge bond between the anthracene moieties. Theoretical simulations illustrate the mechanism of the chemical reaction, highlighting three major steps: dehalogenation, diffusion of surface‐stabilized carbenes, and homocoupling, which enables the formation of an ethynylene bridge. Our results introduce a novel chemical protocol to design π‐conjugated polymers based on oligoacene precursors and pave new avenues for advancing the emerging field of on‐surface synthesis. 相似文献
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Fabian Schulz Ftima García Katharina Kaiser Dolores Prez Enrique Guitin Leo Gross Diego Pea 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(27):9136-9140
A route to generate cyclacenes by on‐surface synthesis is explored. We started by synthesizing two tetraepoxycyclacenes by sequences of Diels–Alder cycloadditions. Subsequently, these molecules were deposited onto Cu(111) and scanning‐tunneling‐microscopy(STM)‐based atom manipulation was employed to dissociate the oxygen atoms. Atomic force microscopy (AFM) with CO‐functionalized tips enabled the detailed characterization of the reaction products and revealed that, at most, two oxygens per molecule could be removed. Importantly, our experimental results suggest that the generation of cyclacenes by the described route might be possible for larger epoxycyclacenes. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(39):12107-12110
Acenes are intriguing molecules with unique electronic properties. The difficulties in their preparation owing to low stability under ambient conditions are apparent because successful syntheses of long unsubstituted acenes are still scarce, in spite of the great attention they have attracted. Only unsubstituted acenes up to heptacene have been isolated in bulk, with nonacene being the largest acene detected to date. Herein we use on‐surface assisted reduction of tetraepoxy decacene precursors on Au(111) as the key step to generate unprecedented decacene which is visualized and its electronic resonances studied by scanning tunneling microscopy (STM) and spectroscopy (STS). 相似文献
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Guoqiang Shi Junfeng Zhou Zhuo Li Ye Sun Lev N. Kantorovich Qiang Fang Flemming Besenbacher Miao Yu 《Angewandte Chemie (International ed. in English)》2020,59(37):15958-15962
Developing graphene‐like two‐dimensional materials naturally possessing a band gap has sparked enormous interest. Thanks to the inherent wide band gap and high mobility in the 2D plane, covalent organic frameworks containing triazine rings (t‐COFs) hold great promise in this regard, whilst the synthesis of single‐layer t‐COFs remains highly challenging. Herein, we present the fabrication of a well‐defined graphene‐like t‐COF on Au(111). Instead of single/multiple‐step single‐type reactions commonly applied for on‐surface synthesis, distinct stepwise on‐surface reactions, including alkynyl cyclotrimerization, C?O bond cleavage, and C?H bond activation, are triggered on demand, leading to product evolution in a controlled step‐by‐step manner. Aside from the precise control in sophisticated on‐surface synthesis, this work proposes a single‐atomic‐layer organic semiconductor with a wide band gap of 3.41 eV. 相似文献
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Cover Picture: Comparing Ullmann Coupling on Noble Metal Surfaces: On‐Surface Polymerization of 1,3,6,8‐Tetrabromopyrene on Cu(111) and Au(111) (Chem. Eur. J. 17/2016) 下载免费PDF全文
Dr. Tuan Anh Pham Dr. Fei Song Dr. Manh‐Thuong Nguyen Dr. Zheshen Li Florian Studener Prof. Meike Stöhr 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5797-5797
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新型SiBNC陶瓷先驱体——聚硼硅氮烷的合成与表征 总被引:6,自引:1,他引:5
以甲基氢二氯硅烷、三氯化硼、六甲基二硅氮烷为起始原料, 采用共缩合的方法合成了一种新型的可溶可熔的SiBNC陶瓷先驱体--聚硼硅氮烷(PBSZ). 该法合成工艺简单, 且合成收率约为91% (w%). 采用元素分析、傅立叶红外光谱、核磁共振波谱、X射线光电子能谱、动态热机械分析、热重分析等对PBSZ的组成、结构和性能进行了表征. 结果表明, 先驱体的主要骨架为-Si-N-B-, 其中, B, N以硼氮六环形式存在, 而C则以Si-CH3形式存在. 该先驱体熔点为69 ℃, 数均分子量为10802, 分子量分散系数为1.50. 此外, 所合成的先驱体具有优良的成型性, 在80 ℃的N2气氛中可纺丝得到15~20 μm的有机纤维, 1000 ℃时相应陶瓷产率约为63% (w%). 相似文献
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以氨丙基硅胶为核,通过与丙烯酸甲酯和乙二胺进行多次重复的Michael加成反应以及酰胺化反应制得在硅胶表面接枝的树枝状大分子(G);G进一步通过L-苯丙氨酸(L-Phe)的手性修饰得到在硅胶表面接枝的手性树枝状大分子(G-L-Phe).G和G-L-Phe的结构经~(13)C NMR,IR及SEM表征. 相似文献