- Defective Nanographenes Containing Seven-Five-Seven (7-5-7)-Membered Rings
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Defects have been observed in graphene and are expected to play a key role in its optical, electronic, and magnetic properties. However, because most of the studies focused on the structural characterization, the implications of topological defects on the physicochemical properties of graphene remain poorly understood. Here, we demonstrate a bottom-up synthesis of three novel nanographenes (1-3) with well-defined defects in which seven-five-seven (7-5-7)-membered rings were introduced to their sp2 carbon frameworks. From the X-ray crystallographic analysis, compound 1 adopts a nearly planar structure. Compound 2, with an additional five-membered ring compared to 1, possesses a slightly saddle-shaped geometry. Compound 3, which can be regarded as the "head-to-head"fusion of 1 with two bonds, features two saddles connected together. The resultant defective nanographenes 1-3 were well-investigated by UV-vis absorption, cyclic voltammetry, and time-resolved absorption spectra and further corroborated by density functional theory (DFT) calculations. Detailed experimental and theoretical investigations elucidate that these three nanographenes 1-3 exhibit an anti-aromatic character in their ground states and display a high stability under ambient conditions, which contrast with the reported unstable biradicaloid nanographenes that contain heptagons. Our work reported herein offers insights into the understanding of structure-related properties and enables the control of the electronic structures of expanded nanographenes with atomically precise defects.
- Fei, Yiyang,Fu, Yubin,Bai, Xueqin,Du, Lili,Li, Zichao,Komber, Hartmut,Low, Kam-Hung,Zhou, Shengqiang,Phillips, David Lee,Feng, Xinliang,Liu, Junzhi
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- A novel chromatism switcher with double receptors selectively for Ag + in neutral aqueous solution: 4,5-diaminoalkeneamino-N-alkyl-l,8- naphthalimides
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Two novel fluorosensors of 4,5-disubstituted-N-alkyl-l,8-naphthalimide derivatives (H1, H2, H3) with double ethylenediamino receptors, double propylenediamino receptors, or one methylpiperazine receptor were synthesized, respectively. Their fluorescence and absorption in the presence or absence of nine metal ions were studied. In the presence of Ag+, H1's absorption moved to long wavelength with color change from yellow-green to red, its quenching and red shift in fluorescence were also remarkable. Similarly, H1's fluorescence was also strongly quenched in the presence of Cu2+. In addition, H1 and H2 show high pH sensitively. There was 139-folds fluorescence enhancement for H1, 22-folds for H2, and 4-folds for H3 when pH was changed from 8 to 3, respectively.
- Jia, Lihua,Zhang, Yu,Guo, Xiangfeng,Qian, Xuhong
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- Spatial anion control on palladium for mild C-H arylation of arenes
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C-H arylation of arenes without the use of directing groups is a challenge, even for simple molecules, such as benzene. We describe spatial anion control as a concept for the design of catalytic sites for C-H bond activation, thereby enabling nondirected C-H arylation of arenes at ambient temperature. The mild conditions enable late-stage structural diversification of biologically relevant small molecules, and site-selectivity complementary to that obtained with other methods of arene functionalization can be achieved. These results reveal the potential of spatial anion control in transition-metal catalysis for the functionalization of C-H bonds under mild conditions.
- Dhankhar, Jyoti,González-Fernández, Elisa,Dong, Chao-Chen,Mukhopadhyay, Tufan K.,Linden, Anthony,?ori?, Ilija
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supporting information
p. 19040 - 19046
(2020/11/13)
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- Synthesis of corannulene and alkyl derivatives of corannulene
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Synthesis of corannulene and alkyl corannulene derivatives has been accomplished using solution-phase chemistry. The key step in the synthesis is the coupling of benzylic bromides of 1,6,7,10-tetraalkylfluoranthene derivatives by low-valent titanium to construct the corannulene nucleus. The use of low-valent titanium represents a viable alternative to flash vacuum pyrolysis methods previously developed. Corannulene (1), methylcorannulene (8), three different dimethylcorannulenes (2, 3, 5), two different tetramethylcorannulenes (4, 6), acecorannulylene (7), C5h symmetric pentamethylcorannulene (9), and decamethylcorannulene (10) have been prepared using low-valent titanium carbon-carbon coupling chemistry and halogen for alkyl exchange chemistry mediated by trimethylaluminum and catalytic nickel salts.
- Seiders, T. Jon,Elliott, Eric L.,Grube, Gunther H.,Siegel, Jay S.
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p. 7804 - 7813
(2007/10/03)
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- 3,4-DICHALCOGEN-BRIDGED FLUORANTHENES AS NEW ELECTRON DONORS
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Three 3,4-dichalcogen-bridged fluoranthenes were prepared with a view of developing new electron donors.Their donor strength was observed to increase in order of the chalcogen triad, i.e., sulfur, selenium, and tellurium.
- Miyamoto, Hisakazu,Yui, Koji,Aso, Yoshio,Otsubo, Tetsuo,Ogura, Fumio
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p. 2011 - 2014
(2007/10/02)
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