Complejos metálicos biestables para la electrónica molecular: síntesis y organización sobre superficies de rotaxanos y moléculas imán

RESUMEN En Capítulo 1 se aborda la síntesis de un nuevo sistema biestable basado en un rotaxano coordinado de cobre, incorporando en el fragmento lineal unidades de terpiridina y fenantrolina directamente enlazadas por sus posiciones T5 y F3 así como los intentos de utilizarlo en la construcción de un rotaxano biestable. En el Capítulo 2 se demuestra la posibilidad de utilizar un conjugado de 3,5-fenantrolina terpiridina (L) en la construcción de diferentes sistemas de interés. En una primera parte, se presenta la síntesis una serie de nuevos complejos luminiscentes mono-, di- y trinucleares basados en Ru/Os, estudiándose sus propiedades de absorción y emisión, así como los tiempos de vida del estado excitado. En la segunda parte, la naturaleza heteroditópica de L se explota en el diseño de sistemas metalosupramoleculares: cajas y polígonos moleculares, homo- y heterometálicos, con índices de coordinación variables. En el Capítulo 3 se presenta una estrategia que permite la deposición con precisión nanométrica de derivados catiónicos de la molécula imán Mn12 sobre superficies de silicio. El método combina la utilización de la técnica de oxidación local y las interacciones electrostáticas entre la molécula y una superficie funcionalizada. ____________________________________________________________________________________________________In Chapter 1 the synthesis of a rigid linear ligand based on directly connected phenanthroline and terpyridine units by means of their T5 and F3 positions is presented accompanied by our attempts to use the ligand in the construction of a bistable rotaxane. In Chapter 2, the feasibility of using a 3,5-phenanthroline terpyridine conjugate (L) for the construction of different systems of interest is demonstrated. In the first part, the synthesis of a series of new luminescent mono-, di- and trinuclear Ru/Os complexes is presented; their absortion, emission and excited state lifetimes have also been studied. In the second part, the heteroditopic nature of L is exploited in the design of metallosupramolecular systems: molecular cages and homo- and heterometallic polygons with variable coordination indexes and finally in Chapter 3 a strategy for the deposition over silicon surfaces of cationic Mn12 derivative single molecule magnets with nanometric precision is presented. This method combines the use of local oxidation nanolithography and the electrostatic between the molecule and a functionalized monolayer

Optimization of 3-DOF Parallel Motion Devices for Low-Cost Vehicle Simulators

Motion generation systems are becoming increasingly important in certain Virtual Reality (VR) applications, such as vehicle simulators. This paper deals with the analysis of the Inverse Kinematics (IK) and the reachable workspace of a three-degrees-of-freedom (3-DOF) parallel manipulator, proposing different transformations and optimizations in order to simplify its use with Motion Cueing Algorithms (MCA) for self-motion generation in VR simulators. The proposed analysis and improvements are performed on a 3-DOF heave-pitch-roll manipulator with rotational motors, commonly used for low-cost motion-based commercial simulators. The analysis has been empirically validated against a real 3-DOF parallel manipulator in our labs using an optical tracking system. The described approach can be applied to any kind of 3-DOF parallel manipulator, or even to 6-DOF parallel manipulators. Moreover, the analysis includes objective measures (safe zones) on the workspace volume that can provide a simple but efficient way of comparing the kinematic capabilities of different kinds of motion platforms for this particular application

A Multi-Projector Calibration Method for Virtual Reality Simulators with Analytically Defined Screens

The geometric calibration of projectors is a demanding task, particularly for the industry of virtual reality simulators. Different methods have been developed during the last decades to retrieve the intrinsic and extrinsic parameters of projectors, most of them being based on planar homographies and some requiring an extended calibration process. The aim of our research work is to design a fast and user-friendly method to provide multi-projector calibration on analytically defined screens, where a sample is shown for a virtual reality Formula 1 simulator that has a cylindrical screen. The proposed method results from the combination of surveying, photogrammetry and image processing approaches, and has been designed by considering the spatial restrictions of virtual reality simulators. The method has been validated from a mathematical point of view, and the complete system which is currently installed in a shopping mall in Spain has been tested by different users

Metal Node Control of Brønsted Acidity in Heterobimetallic Titanium–Organic Frameworks

Compared to indirect framework modification, synthetic control of cluster composition can be used to gain direct access to catalytic activities exclusive of specific metal combinations. We demonstrate this concept by testing the aminolysis of epoxides with a family of isostructural mesoporous frameworks featuring five combinations of homometallic and heterobimetallic metal-oxo trimers (Fe3, Ti3, TiFe2, TiCo2, and TiNi2). Only TiFe2 nodes display activities comparable to benchmark catalysts based on grafting of strong acids, which here originate from the combination of Lewis Ti4+ and Brønsted Fe3+–OH acid sites. The applicability of MUV-101(Fe) to the synthesis of β-amino alcohols is demonstrated with a scope that also includes the gram scale synthesis of propranolol, a natural β-blocker listed as an essential medicine by the World Health Organization, with excellent yield and selectivity

Surface Functionalization of Metal-Organic Framework Crystals with Catechol Coatings for Enhanced Moisture Tolerance

Robust catechol coatings for enhanced moisture tolerance were produced in one step by direct reaction of Hong Kong University of Science and Technology (HKUST) with synthetic catechols. We ascribe the rapid formation of homogeneous coatings around the metal-organic framework particles to the biomimetic catalytic activity of Cu(II) dimers in the external surface of the crystals. Use of fluorinated catechols results in hydrophobic, permeable coatings that protect HKUST from water degradation while retaining close to 100% of its original sorption capacity

Local Oxidation Nanolithography on Metallic Transition Metal Dichalcogenides Surfaces

The integration of atomically-thin layers of two dimensional (2D) materials in nanodevices demands for precise techniques at the nanoscale permitting their local modification, structuration or resettlement. Here, we present the use of Local Oxidation Nanolithography (LON) performed with an Atomic Force Microscope (AFM) for the patterning of nanometric motifs on different metallic Transition Metal Dichalcogenides (TMDCs). We show the results of a systematic study of the parameters that affect the LON process as well as the use of two different modes of lithographic operation: dynamic and static. The application of this kind of lithography in different types of TMDCs demonstrates the versatility of the LON for the creation of accurate and reproducible nanopatterns in exfoliated 2D-crystals and reveals the influence of the chemical composition and crystalline structure of the systems on the morphology of the resultant oxide motifs

Surface Functionalization of Metal-Organic Frameworks for Improved Moisture Resistance

Metal-organic frameworks (MOFs) are a class of porous inorganic materials with promising properties in gas storage and separation, catalysis and sensing. However, the main issue limiting their applicability is their poor stability in humid conditions. The common methods to overcome this problem involve the formation of strong metal-linker bonds by using highly charged metals, which is limited to a number of structures, the introduction of alkylic groups to the framework by post-synthetic modification (PSM) or chemical vapour deposition (CVD) to enhance overall hydrophobicity of the framework. These last two usually provoke a drastic reduction of the porosity of the material. These strategies do not permit to exploit the properties of the MOF already available and it is imperative to find new methods to enhance the stability of MOFs in water while keeping their properties intact. Herein, we report a novel method to enhance the water stability of MOF crystals featuring Cu2(O2C)4 paddle-wheel units, such as HKUST (where HKUST stands for Hong Kong University of Science & Technology), with the catechols functionalized with alkyl and fluoro-alkyl chains. By taking advantage of the unsaturated metal sites and the catalytic catecholase-like activity of CuII ions, we are able to create robust hydrophobic coatings through the oxidation and subsequent polymerization of the catechol units on the surface of the crystals under anaerobic and water-free conditions without disrupting the underlying structure of the framework. This approach not only affords the material with improved water stability but also provides control over the function of the protective coating, which enables the development of functional coatings for the adsorption and separations of volatile organic compounds. We are confident that this approach could also be extended to other unstable MOFs featuring open metal sites

Origin of the Chemiresistive Response of Ultrathin Films of Conductive Metal-Organic Frameworks

Conductive metal-organic frameworks are opening new perspectives for the use of these porous materials for applications traditionally limited to more classical inorganic materials, such as their integration into electronic devices. This has enabled the development of chemiresistive sensors capable of transducing the presence of specific guests into an electrical response with good selectivity and sensitivity. By combining experimental data with computational modelling, a possible origin for the underlying mechanism of this phenomenon in ultrathin films (ca. 30 nm) of Cu‐CAT‐1 is described

Bioinspired catechol-terminated self-assembled monolayers with enhanced adhesion properties

The role of the catechol moiety in the adhesive properties of mussel proteins and related synthetic materials has been extensively studied in the last years but still remains elusive. Here, a simplified model approach is presented based on a self-assembled monolayer (SAM) of upward-facing catechols thiol-bound to epitaxial gold substrates. The orientation of the catechol moieties is confirmed by spectroscopy, which also showed lack of significant amounts of interfering o-quinones. Local force-distance curves on the SAM measured by atomic force microscopy (AFM) shows an average adhesion force of 45 nN, stronger than that of a reference polydopamine coating, along with higher reproducibility and less statistical dispersion. This is attributed to the superior chemical and topographical homogeneity of the SAM coating. Catechol-terminated SAMs are also obtained on high-roughness gold substrates that show the ability to assemble magnetic nanoparticles, despite their lack of enhanced adhesion at the molecular level. Finally, the influence of the catechol group on the formation and quality of the SAM is explored both theoretically (molecular dynamics simulations) and experimentally using direct-write AFM lithography.This work was supported by MICINN through projects MAT2012–38318-C03–02, MAT2012–38319-C02–01, CTQ2010–15380 and CONSOLIDER NANOSELECT CSD 2007–00041. M. G. thanks the CSIC for a predoctoral grant.Peer Reviewe