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      Versatile synthesis and enlargement of functionalized distorted heptagon-containing nanographenes†

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          Abstract

          Straightforward path to curved graphene molecules: distorted polycyclic aromatic hydrocarbons including heptagon moieties are obtained from simple precursors.

          Abstract

          Highly distorted polycyclic aromatic hydrocarbons (PAHs) are predicted to be attractive goals in nanoscience owing to the new properties they can exhibit. We have shown that a variety of functionalized distorted heptagon-containing nanographenes can be easily prepared from simple building blocks by a sequence of Co-catalyzed cyclotrimerization and cyclodehydrogenation reactions. The versatility of this strategy allows easy subsequent enlargement of these nanostructures by Ni-catalyzed cross-coupling and final cyclodehydrogenation reactions. Soluble extended distorted nanographenes 1 and 2 containing heptagon and an edge-shared pentagon–heptagon combination have been synthesized. High distortion of the polycyclic backbone of 2 caused by non-hexagonal rings and a helicene moiety was confirmed by X-ray crystallography. Experimental data reveal promising optical and electronic properties for distorted PAHs with long fluorescence lifetimes (up to 14.5 ns) and low band gaps (down to 2.27 eV). This straightforward and versatile synthetic strategy, the observed long fluorescence lifetimes and the small optical and electrochemical band gaps for the presented compounds may promote the future implementation of distorted graphene molecules in electronic devices.

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          A grossly warped nanographene and the consequences of multiple odd-membered-ring defects.

          Graphite, the most stable form of elemental carbon, consists of pure carbon sheets stacked upon one another like reams of paper. Individual sheets, known as graphene, prefer planar geometries as a consequence of the hexagonal honeycomb-like arrangements of trigonal carbon atoms that comprise their two-dimensional networks. Defects in the form of non-hexagonal rings in such networks cause distortions away from planarity. Herein we report an extreme example of this phenomenon. A 26-ring C80H30 nanographene that incorporates five seven-membered rings and one five-membered ring embedded in a hexagonal lattice was synthesized by stepwise chemical methods, isolated, purified and fully characterized spectroscopically. Its grossly warped structure was revealed by single-crystal X-ray crystallography. An independent synthetic route to a freely soluble derivative of this new type of 'nanocarbon' is also reported. Experimental data reveal how the properties of such a large graphene subunit are affected by multiple odd-membered-ring defects.
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            New fluorescent probes for sulfane sulfurs and the application in bioimaging.

            A sulfane sulfur mediated benzodithiolone formation was developed. Based on this reaction, two fluorescent probes (SSP1 and SSP2) for the detection of sulfane sulfur species (persulfide, polysulfide, and elemental sulfur) were prepared and evaluated. The probes showed high selectivity and sensitivity to sulfane sulfurs. Moreover, SSP2 was successfully applied for bioimaging sulfane sulfurs in living cells.
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              Quantum transport in graphene nanoribbons: effects of edge reconstruction and chemical reactivity.

              We present first-principles transport calculations of graphene nanoribbons with chemically reconstructed edge profiles. Depending on the geometry of the defect and the degree of hydrogenation, spectacularly different transport mechanisms are obtained. In the case of monohydrogenated pentagon (heptagon) defects, an effective acceptor (donor) character results in strong electron-hole conductance asymmetry. In contrast, weak backscattering is obtained for defects that preserve the benzenoid structure of graphene. Based on a tight-binding model derived from ab initio calculations, evidence for large conductance scaling fluctuations are found in disordered ribbons with lengths up to the micrometer scale.
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                Author and article information

                Journal
                Chem Sci
                Chem Sci
                Chemical Science
                Royal Society of Chemistry
                2041-6520
                2041-6539
                01 February 2017
                31 August 2016
                : 8
                : 2
                : 1068-1074
                Affiliations
                [a ] Departamento Química Orgánica , Universidad de Granada (UGR) , C. U. Fuentenueva , 18071 Granada , Spain . Email: araceligc@ 123456ugr.es
                [b ] Departamento de Fisicoquímica , Facultad de Farmacia , UGR. Cartuja Campus , 18071 Granada , Spain
                [c ] Departamento de Química Orgánica I , Universidad del País Vasco , E-20018 , San Sebastián , Spain
                [d ] Departamento de Química , Universidad Autónoma de Madrid , c/Francisco Tomás y Valiente no. 7, Cantoblanco , 28049 Madrid , Spain
                [e ] Laboratorio de Estudios Cristalográficos , Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR) , 18100 Armilla , Granada , Spain
                [f ] Departamento de Electrónica y Tecnología de Computadores , Facultad de Ciencias , CITIC , UGR , E-18071 Granada , Spain
                [g ] Fundación IMDEA Nanociencia , Ciudad Universitaria de Cantoblanco , E-28049 Madrid , Spain
                [h ] Institute of Chemical Research of Catalonia (ICIQ) , Catalan Institution for Research and Advanced Studies (ICREA) , Spain
                Author information
                http://orcid.org/0000-0001-5483-5642
                Article
                c6sc02895k
                10.1039/c6sc02895k
                5357993
                28451246
                f5f464de-b078-4e30-82d5-b263cb406242
                This journal is © The Royal Society of Chemistry 2016

                This is an Open Access article distributed under the terms of the Creative Commons Attribution 3.0 Unported License ( http://creativecommons.org/licenses/by/3.0/) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 30 June 2016
                : 30 August 2016
                Categories
                Chemistry

                Notes

                †Electronic supplementary information (ESI) available: General details, synthesis and spectroscopy data of new compounds and copies of 1H and 13C-NMR spectra of new compounds. Experimental details on optical and electrochemical measurements. Crystal data and structure refinement of compounds 2, 6a, 6d and 6h. Further details on theoretical calculations and Cartesian coordinates of computed structures. VT- 1H-NMR, 2D-NMR and HRMS spectra of compounds 1 and 2. CCDC 1485682–1485685. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6sc02895k


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