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Publisher: Cambridge : RSC × Subject: Electronic properties ×

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    Wave-shaped polycyclic hydrocarbons with controlled aromaticity
    (Cambridge : RSC, 2019) Ma, Ji; Zhang, Ke; Schellhammer, Karl Sebastian; Fu, Yubin; Komber, Hartmut; Xu, Chi; Popov, Alexey A.; Hennersdorf, Felix; Weigand, Jan J.; Zhou, Shengqiang; Pisula, Wojciech; Ortmann, Frank; Berger, Reinhard; Liu, Junzhi; Feng, Xinliang
    Controlling the aromaticity and electronic properties of curved π-conjugated systems has been increasingly attractive for the development of novel functional materials for organic electronics. Herein, we demonstrate an efficient synthesis of two novel wave-shaped polycyclic hydrocarbons (PHs) 1 and 2 with 64 π-electrons. Among them, the wave-shaped π-conjugated carbon skeleton of 2 is unambiguously revealed by single-crystal X-ray crystallography analysis. The wave-shaped geometry is induced by steric congestion in the cove and fjord regions. Remarkably, the aromaticity of these two structural isomers can be tailored by the annulated direction of cyclopenta[b]fluorene units. Isomer 1 (Eoptg = 1.13 eV) behaves as a closed-shell compound with weakly antiaromatic feature, whereas its structural isomer 2 displays a highly stable tetraradical character (y0 = 0.23; y1 = 0.22; t1/2 = 91 days) with a narrow optical energy gap of 0.96 eV. Moreover, the curved PH 2 exhibits remarkable ambipolar charge transport in solution-processed organic thin-film transistors. Our research provides a new insight into the design and synthesis of stable functional curved aromatics with multiradical characters. © The Royal Society of Chemistry.
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    Controlling the speciation and reactivity of carbon-supported gold nanostructures for catalysed acetylene hydrochlorination
    (Cambridge : RSC, 2018) Kaiser, Selina K.; Lin, Ronghe; Mitchell, Sharon; Fako, Edvin; Krumeich, Frank; Hauert, Roland; Safonova, Olga V.; Kondratenko, Vita A.; Kondratenko, Evgenii V.; Collins, Sean M.; Midgley, Paul A.; López, Núria; Pérez-Ramírez, Javier
    Carbon-supported gold catalysts have the potential to replace the toxic mercuric chloride-based system applied industrially for acetylene hydrochlorination, a key technology for the manufacture of polyvinyl chloride. However, the design of an optimal catalyst is essentially hindered by the difficulties in assessing the nature of the active site. Herein, we present a platform of carbon supported gold nanostructures at a fixed metal loading, ranging from single atoms of tunable oxidation state and coordination to metallic nanoparticles, by varying the structure of functionalised carbons and use of thermal activation. While on activated carbon particle aggregation occurs progressively above 473 K, on nitrogen-doped carbon gold single atoms exhibit outstanding stability up to temperatures of 1073 K and under reaction conditions. By combining steady-state experiments, density functional theory, and transient mechanistic studies, we assess the relation between the metal speciation, electronic properties, and catalytic activity. The results indicate that the activity of gold-based catalysts correlates with the population of Au(i)Cl single atoms and the reaction follows a Langmuir-Hinshelwood mechanism. Strong interaction with HCl and thermodynamically favoured acetylene activation were identified as the key features of the Au(i)Cl sites that endow their superior catalytic performance in comparison to N-stabilised Au(iii) counterparts and gold nanoparticles. Finally, we show that the carrier (activated carbon versus nitrogen-doped carbon) does not affect the catalytic response, but determines the deactivation mechanism (gold particle aggregation and pore blockage, respectively), which opens up different options for the development of stable, high-performance hydrochlorination catalysts. © 2019 The Royal Society of Chemistry.