A surface confined yttrium(III) bis-phthalocyaninato complex: a colourful switch controlled by electrons

AMs of a Y(III) double-decker complex on ITO have been prepared and their electrical and optical properties explored, exhibiting three accessible stable redox states with characteristic absorption bands in the visible spectra, corresponding to three complementary colors (i.e., green, blue and red). These absorption bands are exploited as output signals of this robust ternary electrochemical switch, behaving hence as an electrochromic molecular-based device.This work was funded by ERC StG 2012-306826 e-GAMES, the EU project ITN iSwitch (GA no. 642196), the Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), DGI (Spain) BE-WELL CTQ2013-40480-R, and Generalitat de Catalunya 2014-SGR-17. I. A. acknowledges CIBER-BBN for a grant.Peer reviewe

A Rapid, Low-Cost, and Scalable Technique for Printing State-of-the-Art Organic Field-Effect Transistors

In 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.This work was mainly funded by the ERC StG 2012 306826 e GAMES and ERC PoC 2014 640120 LAB TECH projects. The authors also thank the Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER BBN), the DGI (Spain) project BE WELL CTQ2013 40480 R, the Generalitat de Catalunya (2014 SGR 17) and the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV 2015 0496). The authors would like to thank the ICTS "NANBIOSIS", more specifically to the Nanotechnology Platform, unit of CIBER BBN at the Institute for Bioengineering of Catalonia (IBEC) for their assistance in ToF SIMS analyses. I. T. acknowledges FPU fellowship from the Ministery and the Materials Science PhD Program of Universitat Autònoma de Barcelona. F. G. D. P. thanks Universidad Técnica de Ambato and Secretaría de Educación Superior, Ciencia, Tecnología e Innovación for funding through a doctoral scholarship “Convocatoria abierta 2010”.Peer reviewe

High Performance Organic Field-Effect Transistors with Solid and Aqueous Dielectric Based on a Solution Sheared Sulfur-Bridged Annulene Derivative

Thin 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

Direct covalent grafting of an organic radical core on gold and silver

The 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

Extensive study of the electron donor 1,1,4,4-tetrathiabutadiene (TTB) and of its charge transfer crystal with TCNQ

In 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

Self-Assembly of an Organic Radical Thin Film and its Memory Function Investigated Using a Liquid Metal Electrode

In 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

Neutral organic radical formation by chemisorption on metal surfaces

Organic 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 (1•) 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 1•. 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•.This work was funded by ERC StG 2012-306826 e-GAMES, the European Regional Development Fund (ERDF) under the program Interreg V-A España-Francia-Andorra (contract no. EFA 194/16 TNSI), the Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine (CIBERBBN), the Spanish Ministry of Economy and Competitiveness (MINECO/FEDER) through projects FANCY CTQ2016-80030-R, RTI2018-095460-B-I00 and MAT2016-78293-C6-2-R, the “Severo Ochoa” Programme for Centers of Excellence in R&D (SEV-2015-0496 and SEV-2017-0706), and the “Maria de Maeztu” program for Spanish Structures of Excellence (MDM-2017-0767). This research was also supported in part by Generalitat de Catalunya (grants 2017SGR13 and 2017SGR918). Computational time was provided by through grants from the Red Española de Supercomputacion. I.A. acknowledges the Spanish Ministerio de Educacion Cultura y Deporte for an FPU Ph.D. scholarship, and F.I. acknowledges additional support from a 2015 ICREA Academia Award. This research was also funded by the CERCA Programme/Generalitat de Catalunya. C.M. was supported by the Agency for Management of University and Research grants (AGAUR) of the Catalan government through the FP7 framework program of the European Commission under Marie Curie COFUND action 600385.Peer reviewe

Highly Oxidized States of Phthalocyaninato Terbium(III) Multiple-Decker Complexes Showing Structural Deformations, Biradical Properties and Decreases in Magnetic Anisotropy

Presented 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