50 research outputs found
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
‐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
High Performance Organic Field-Effect Transistors with Solid and Aqueous Dielectric Based on a Solution Sheared Sulfur-Bridged Annulene Derivative
No full textThin films of the organic semiconductor meso-diphenyl tetrathia[22]annulene[2,1,2,1] (DPTTA) are prepared for the first time employing solution-based techniques to fabricate organic field-effect transistors (OFETs). Homogeneous and crystalline films of this semiconductor are achieved, thanks to the synergic approach of employing blends of this material with polystyrene (PS) and the high throughput technique bar-assisted meniscus shearing (BAMS) with a hydrophobic bar. The resulting active layers exhibit state-of-the-art OFET performance with an average mobility of 1 cm2 V−1 s−1, threshold voltage close to 0 V, high on/off ratio, and sharp switch on. Furthermore, a DPTTA:PS formulation is optimized to prepare films suitable for their integration in electrolyte-gated field effect transistors operating in ultrapure water and 0.5 m NaCl aqueous solution. Such devices also reveal excellent performance with mobility values above 0.1 cm2 V−1 s−1, potentiometric sensitivity ≈200 µV, time response ≈9 ms, and long term stability in ultrapure water. Hence, this work supports the strategy of combining organic semiconductor:polymer blends with BAMS as a powerful route for achieving high performing devices, and also points out DPTTA as a highly promising material to be integrated in organic electronic devices.A.C., Q.Z. and M.R.A. equally contributed to this work. The authors thank the ERC StG2012-306826 e-GAMES project, the DGI (Spain) with project, FANCY CTQ2016-80030-R, the Generalitat de Catalunya (2014-SGR-17), the Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), and the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2015-0496). Q.Z. acknowledges the China Scholarship Council, the National Natural Science Foundation (NSF) of China (11404266), and the Fundamental Research Funds for the Central Universities (Grant No. XDJK2014C081). F.L. gratefully acknowledges the “Juan de la Cierva” programme. A.C. and Q.Z. are enrolled in the Materials Science PhD Program of Universitat Autònoma de Barcelona.Peer reviewe
On‐surface synthesis of porous graphene nanoribbons containing nonplanar [14]annulene pores
No full textThe precise introduction of nonplanar pores in the backbone of graphene nanoribbon represents a great challenge. Here, we explore a synthetic strategy toward the preparation of nonplanar porous graphene nanoribbon from a predesigned dibromohexabenzotetracene monomer bearing four cove-edges. Successive thermal annealing steps of the monomers indicate that the dehalogenative aryl-aryl homocoupling yields a twisted polymer precursor on a gold surface and the subsequent cyclodehydrogenation leads to a defective porous graphene nanoribbon containing nonplanar [14]annulene pores and five-membered rings as characterized by scanning tunneling microscopy and noncontact atomic force microscopy. Although the C–C bonds producing [14]annulene pores are not achieved with high yield, our results provide new synthetic perspectives for the on-surface growth of nonplanar porous graphene nanoribbons
Direct covalent grafting of an organic radical core on gold and silver
No full textThe functionalisation of surfaces with organic radicals, such as perchlorotriphenylmethyl (PTM) radicals or tris(2,4,6-trichloro-phenyl)methyl (TTM) radicals, is appealing for the development of molecular spintronic devices. Conventionally, organic radicals are chemisorbed to metal substrates by using long alkyl or aromatic spacers resulting in a weak spin–electron coupling between the radical and the substrate. To circumvent this problem, here we have employed a new design strategy for the fabrication of radical self-assembled monolayers (r-SAMs). This newly designed radical–anchor (R–A) molecule, a TTM based radical disulfide (1), can be easily synthesized and it was here characterized by electron spin resonance (ESR), cyclic voltammetry (CV) and superconducting quantum interference device magnetometry (SQUID). We have succeeded in fabricating TTM based r-SAMs by using thiolate bonds (Au–S and Ag–S) where the TTM cores are only one-atom distance from the metal surface for the first time. The resultant robust 1/Au and 1/Ag r-SAMs were well characterized, and the electrochemical and the magnetic properties were unambiguously confirmed, proving the persistence of the molecular spin.This work was funded by ERC StG 2012-306826 e-GAMES. The
authors also thank ITN iSwitch 642196 project, the Networking
Research Center on Bioengineering, Biomaterials and Nanomedicine
(CIBER-BBN), DGI (Spain) BE-WELL CTQ2013-40480-
R and FANCY CTQ2016-80030-R, and Generalitat de Catalunya
2014-SGR-17. The authors also acknowledge the Spanish
Ministry of Economy and Competitiveness, through the “Severo
Ochoa” Programme for Centres of Excellence in R&D (SEV-2015-
0496). We thank Dr V. Lloveras for ESR spectroscopy characterization,
Mr A. Bernab´e for MALDI-TOF measurements and Dr
G. Sauthier from ICN2 for XPS and UPS measurements. We also
thank Dr N. Crivillers for useful discussions. S. T. B. and I. A.
acknowledge support from the Spanish MINECO grant
CTQ2015-64618-R grant and, in part, by Generalitat de Catalunya
grants 2014SGR97 and XRQTC. IA acknowledges the
Spanish Ministerio de Educaci´on Cultura y Deporte for a FPU
PhD scholarship. Access to supercomputer resources as provided through grants from the Red Espanola de Supercomputación is also acknowledged.Peer reviewe
Neutral organic radical formation by chemisorption on metal surfaces
No full textOrganic radical monolayers (r-MLs) bonded to metal surfaces are potential materials for the development of molecular (spin)electronics. Typically, stable radicals bearing surface anchoring groups are used to generate r-MLs. Following a recent theoretical proposal based on a model system, we report the first experimental realization of a metal surface-induced r-ML, where a rationally chosen closed-shell precursor 3,5-dichloro-4-[bis(2,4,6-trichlorophenyl)methylen]cyclohexa-2,5-dien-1-one (1) transforms into a stable neutral open-shell species () via chemisorption on the Ag(111) surface. X-ray photoelectron spectroscopy reveals that the >C=O group of 1 reacts with the surface, forming a C-O-Ag linkage that induces an electronic rearrangement that transforms 1 to . We further show that surface reactivity is an important factor in this process whereby Au(111) is inert towards 1, whereas the Cu(111) surface leads to dehalogenation reactions. The radical nature of the Ag(111)-bound monolayer was further confirmed by angle-resolved photoelectron spectroscopy and electronic structure calculations, which provide evidence of the emergence of the singly occupied molecular orbital (SOMO) of 1
π-Extended peri-Acenes: Recent Progress in Synthesis and Characterization
No full textIn memory of François Diederich.Nanographenes (NGs) with open-shell character have gained intense attention due to their potential applications in future organic nanoelectronics and spintronics. Among them, NGs bearing a pair of parallel zigzag edges, such as acenes and periacenes (PAs) bestow unique (opto)electronic and magnetic properties owing to their localized non-bonding π-state. However, their reactive zigzag edges impart intrinsic instability, leading to the challenging synthesis. The recent development of synthetic strategies provided access to several π-extended PAs, which were considered unrealistic for decades. Notably, their laterally π-extended structures of zigzag-edged graphene nanoribbons was realised via on-surface synthesis. However, synthesis of π-extended PAs in solution is still in its infancy, more intensive scientific efforts are needed to surpass the existing challenges regarding stability and solubility. This Review provides an overview of recent progress in the synthesis and characterization of PAs through a bottom-up synthetic strategy, including on-surface and solution-phase chemistry. In addition, views on existing challenges and the future prospects are also provided
Light interception and yield response of cotton varieties to high density planting and fertilizers in sub-tropical India
No full textPlant density and optimum fertilization are two important agronomic practices to enhance productivity of cotton (Gossypium hirsutum L.) varieties. The objective of this study was to investigate the effect of high density planting (HDPS) and fertilization rate, especially their interactions, on yield, yield components of cotton varieties in sub-tropical India. Split-split plot design was adopted and replicated thrice. The main plots were assigned to low, medium and high plant densities (16.7, 13.3 and 11.1 plants/m2). Pre released cotton varieties TCH-1705 and LH-2298 were tested in low, moderate and high rates of fertilizers recommended for the region (100, 125 and 150 %) in sub-sub plots. Significantly higher seed cotton yield (1148 kg/ha) was achieved in narrow inter row spaced at 60 cm over normal plant row spacing of 90 cm (1025 kg/ha). Compact genotype TCH-1705 was out yielded (1146 kg/ha) over LH 2298(1044 kg/ha). Application of fertilizers at higher rate improved seed cotton yield (1232 kg/ha) Leaf area index (3.8) and light interception (0.98) over blanket recommendation. The results of the study inferred that seed cotton yield improvement was possible under HDPS production system with compact varieties grown at narrow spacing and higher fertilizer dose
Highly Oxidized States of Phthalocyaninato Terbium(III) Multiple-Decker Complexes Showing Structural Deformations, Biradical Properties and Decreases in Magnetic Anisotropy
No full textPresented here is a comprehensive study of highly oxidized multiple‐decker complexes composed of TbIII and CdII ions and two to five phthalocyaninato ligands, which are stabilized by electron‐donating n‐butoxy groups. From X‐ray structural analyses, all the complexes become axially compressed upon ligand oxidation, resulting in bowl‐shaped distortions of the ligands. In addition, unusual coexistence of square antiprism and square prism geometries around metal ions was observed in +4e charged species. From paramagnetic 1H NMR studies on the resulting series of triple, quadruple and quintuple‐decker complexes, ligand oxidation leads to a decrease in the magnetic anisotropy, as predicted from theoretical calculations. Unusual paramagnetic shifts were observed in the spectra of the +2e charged quadruple and quintuple‐decker complexes, indicating that those two species are actually unexpected triplet biradicals. Magnetic measurements revealed that the series of complexes show single‐molecule magnet properties, which are controlled by the multi‐step redox induced structural changes.This work was financially supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Numbers JP14J02656 (Y.H.), JP20225003 (M.Y.), JP15K05467 (K.K.), JP24750119 (K.K.), 18K14242 (Y.H.), 19K05401(Y.K), Tohoku University Molecule & Material Synthesis Platform in Nanotechnology Platform Project, CREST, JST JPMJCR12L3 (M.Y.), PhD scholarship from the Beilstein‐Institut zur Förderung der Chemischen Wissenschaften (M.D.), the German‐Japanese University Consortium (HeKKSaGOn), the state of Baden‐Württemberg through bwHPC and the German Research Foundation (DFG) through grant no INST 40/467‐1 FUGG (JUSTUS cluster), European Union (ERC StG 2012–306826 e‐GAMES), Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine (CIBER‐BBN), the Spanish Ministry of Economy and Competitiveness (projects FANCY CTQ2016‐80030‐R, MOTHER MAT2016‐80826‐R and the “Severo Ochoa” Programme for Centers of Excellence in R&D, SEV‐2015‐0496), Generalitat de Catalunya (2017SGR918), 111 Project (B18030) from China (M.Y.), the scientific grants R‐143‐000‐A80‐114, R‐143‐000‐A65‐133 from the National University of Singapore. We thank Dr. Norihisa Hoshino for EPR measurements, Dr. Tetsuko Nakaniwa and Prof. Dr. Genji Kurisu and Dr. Takefumi Yoshida for SCXRD measurements. This paper is Contribution No. 62 from the Research Center for Thermal and Entropic Science.Peer reviewe
Self-Assembly of an Organic Radical Thin Film and its Memory Function Investigated Using a Liquid Metal Electrode
No full textIn this work, the deposition of a persistent organic radical by thermal evaporation on gold, platinum and graphene is performed. The impact of the deposition parameters and the nature of the substrate on the molecular organization within the deposited film are investigated. The non-planarity of the molecule and the role of the molecule-molecule and molecule-substrate interactions are discussed. Ultraviolet photoelectron spectroscopy experiments demonstrate that the radical character, and hence its magnetic and redox properties, is preserved on the three surfaces. The optimized films are electrically characterized by top-contacting the film/substrate system using a liquid metal which permits to achieve a soft-contact avoiding damaging the layer. The hysteretic current versus voltage curves obtained from the electrical characterization points to the potential applicability of the studied system as an organic memory. Moreover, the demonstrated feasibility of using a liquid metal is an appealing approach towards the preparation of flexible devices.We thank Dr. Raphael Pfattner for the fruitful discussions. We thank Dr. Guillaume Sauthier from
the Catalan Institute of Nanoscience and Nanotechnology (ICN2) for the XPS measurements. This
work was supported by MINECO through the “Severo Ochoa” Programme for Centers of
Excellence in R&D (SEV-2015-0496) and the FUNMAT-FIP projects, the European Research
Council (ERC) StG 2012-306826 e-GAMES project. The authors also thank the CIBER-BBN, the
Dirección General de Investigación (DGI) (Spain) project FANCY CTQ2016-80030-R and the
Generalitat de Catalunya (2017-SGR-918).Peer reviewe
