7 research outputs found
‐Heptacene: Synthesis and In Situ Characterization
No full textn-peri-Acenes (n-PAs) have gained interest as model systems of zigzag-edged graphene nanoribbons for potential applications in nanoelectronics and spintronics. However, the synthesis of n-PAs larger than peri-tetracene remains challenging because of their intrinsic open-shell character and high reactivity. Presented here is the synthesis of a hitherto unknown n-PA, that is, peri-heptacene (7-PA), in which the reactive zigzag edges are kinetically protected with eight 4-tBu-C6H4 groups. The formation of 7-PA is validated by high-resolution mass spectrometry and in situ FT-Raman spectroscopy. 7-PA displays a narrow optical energy gap of 1.01 eV and exhibits persistent stability (t1/2≈25 min) under inert conditions. Moreover, electron-spin resonance measurements and theoretical studies reveal that 7-PA exhibits an open-shell feature and a significant tetraradical character. This strategy could be considered a modular approach for the construction of next-generation (3 N+1)-PAs (where N≥3). © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH Gmb
Extensive study of the electron donor 1,1,4,4-tetrathiabutadiene (TTB) and of its charge transfer crystal with TCNQ
No full textIn the spirit of the renewed interest in mixed stack charge-transfer (CT) crystals, made up by alternating π electron-donor and acceptor molecules, we focus attention on a forgotten donor, 1,1,4,4-tetrathiabutadiene (TTB), synthesized more than 35 years ago. We present a spectroscopic and computational characterization of the neutral TTB, and fully characterize the CT crystal with TCNQ. TTB-TCNQ is a mixed stack crystal, with limited degree of CT (about 0.1), despite TTB electron donating strength is only a little smaller than that of the famous TTF. This finding is explained by the small value of the Madelung energy, that we evaluate by a well tested computational approach.We thank the late Prof. Daniel J. Sandman for his help with the synthesis. We acknowledge the support of the EU with ERC StG2012-306826e-GAMES and of the MINECO of the Spanish Government (CTQ2016- 80030-R and SEV-2015-0496).Peer reviewe
A rapid, low-cost, and scalable technique for printing state-of-the-art organic field-effcet transistors
No full textIn the last few years exciting advances have been achieved in developing printing techniques for organic semiconductors, and impressive mobility values have been reported for the resulting organic field-effect transistors (OFETs). However, not all these techniques are scalable and some of them require additional crystallization steps. This study reports on the fabrication of OFETs employing blends of four benchmark organic semiconductors with polystyrene and demonstrates that applying the same formulation and experimental conditions for printing them, highly reproducible and uniform crystalline films exhibiting high OFET performance are successfully achieved. It is noted that the mobility values achieved here are not the highest reported for the studied materials; however, they are state-of-the-art values and could be regarded as exceptional considering the low cost and fast speed of the fabrication process involved here.Peer Reviewe
A rapid, low-cost, and scalable technique for printing state-of-the-art organic field-effcet transistors
No full textIn the last few years exciting advances have been achieved in developing printing techniques for organic semiconductors, and impressive mobility values have been reported for the resulting organic field-effect transistors (OFETs). However, not all these techniques are scalable and some of them require additional crystallization steps. This study reports on the fabrication of OFETs employing blends of four benchmark organic semiconductors with polystyrene and demonstrates that applying the same formulation and experimental conditions for printing them, highly reproducible and uniform crystalline films exhibiting high OFET performance are successfully achieved. It is noted that the mobility values achieved here are not the highest reported for the studied materials; however, they are state-of-the-art values and could be regarded as exceptional considering the low cost and fast speed of the fabrication process involved here.Peer ReviewedPostprint (published version
Tailoring Magnetic Features in Zigzag Edged Nanographenes by Controlled Diels Alder Reactions
No full textNanographenes (NGs) with tunable electronic and magnetic properties have attracted enormous attention in the realm of carbon-based nanoelectronics. In particular, NGs with biradical character at the ground state are promising building units for molecular spintronics. However, most of the biradicaloids are susceptible to oxidation under ambient conditions and photolytic degradation, which hamper their further applications. Herein, we demonstrated the feasibility of tuning the magnetic properties of zigzag-edged NGs in order to enhance their stability via the controlled Diels–Alder reactions of peri-tetracene (4-PA). The unstable 4-PA (y0=0.72; half-life, t1/2=3 h) was transformed into the unprecedented benzo-peri-tetracenes (BPTs) by a one-side Diels–Alder reaction, which featured a biradical character at the ground state (y0=0.60) and exhibited remarkable stability under ambient conditions for several months. In addition, the fully zigzag-edged circumanthracenes (CAs) were achieved by two-fold or stepwise Diels–Alder reactions of 4-PA, in which the magnetic properties could be controlled by employing the corresponding dienophiles. Our work reported herein opens avenues for the synthesis of novel zigzag-edged NGs with tailor-made magnetic properties
‐Heptacene on a Metallic Surface
No full textThe synthesis of long n-peri-acenes (n-PAs) is challenging as a result of their inherent open-shell radical character, which arises from the presence of parallel zigzag edges beyond a certain n value. They are considered as π-electron model systems to study magnetism in graphene nanostructures; being potential candidates in the fabrication of optoelectronic and spintronic devices. Here, we report the on-surface formation of the largest pristine member of the n-PA family, i.e. peri-heptacene (n=7, 7-PA), obtained on an Au(111) substrate under ultra-high vacuum conditions. Our high-resolution scanning tunneling microscopy investigations, complemented by theoretical simulations, provide insight into the chemical structure of this previously elusive compound. In addition, scanning tunneling spectroscopy reveals the antiferromagnetic open-shell singlet ground state of 7-PA, exhibiting singlet–triplet spin-flip inelastic excitations with an effective exchange coupling (Jeff) of 49 meV. © 2022 Wiley-VCH GmbH.This project has received funding from Comunidad de Madrid [projects QUIMTRONIC-CM (Y2018/NMT-4783), MAD2D,and NanoMagCost (P2018/NMT-4321)], ERC ConsolidatorGrant (ELECNANO, 766555), and Ministerio de Ciencia,Innovacion y Universidades (projects SpOrQuMat (PGC2018-098613-B-C21), CTQ2017-83531-R, PID2019-108532GB-I00,and CTQ2016-81911-REDT). IMDEA Nanociencia is appreciative of support from the “Severo Ochoa” Programme forCenters of Excellence in R&D (MINECO, grant SEV-2016-0686). The EU Graphene Flagship (Graphene Core 3,881603), ERC Consolidator Grant (T2DCP, 819698), the German Research Foundation (DFG) within the Cluster ofExcellence “Center for Advancing Electronics Dresden (cfaed)and the DFG-SNSF Research Project (EnhanTopo, No.429265950) are acknowledged for financial support. Weappreciate funding from the Praemium Academie of the Academy of Science of the Czech Republic and the CzechNa-noLab Research Infrastructure supported by MEYS CR(LM2018110). P.J. thanks the support of the GACR 2013692X. J.I.U. acknowledges the European Union’s Horizon2020 research and innovation programme under the MarieSkłodowska-Curie grant agreement No [886314].Peer reviewe
