Un univers en miniatura: Els reptes de la nanociència molecular

Miniature Universe: Challenges Facing Molecular Nanoscience.The molecular fi eld of Nanoscience is an area as yet little explored in Nanoscience. This may be because, compared to simpler atom-based nano-objects, the larger structural and electronic complexity of molecules makes them more diffi cult to study at nanoscale with the instrumentaltechniques available today. Nonetheless, it is in this molecular fi eld where molecular chemists, biologists, physicists and engineers working in Nanosciences may have the best opportunities to interact. Areas like supramolecular chemistry, molecular electronics and molecular magnetismare expected to converge in this area. Here, the author gives the examples of bio-magnetic nanomaterials and multifunctional magnetic materials to illustrate the opportunities provided by this emergent area in chemistry, physics and materials science

Magnetic Functionalities in MOFs: from the Framework to the Pore

In this review, we show the different approaches so far developed to prepare Metal-Organic Frameworks (MOFs) presenting electronic functionalities, with particular attention to magnetic properties. We will cover the chemical design of the framework necessary for the incorporation of different magnetic phenomena, as well as the encapsulation of functional species in the pores leading to hybrid multifunctional MOFs combining an extended lattice with a molecular lattice

Hybrid nanostructures based on gold nanoparticles and functional coordination polymers: Chemistry, physics and applications in biomedicine, catalysis and magnetism

During the last decade, the scientific community has become interested in hybrid nanomaterials, especially the ones that combine gold nanoparticles with a second functional component. In this context, coordination polymers are materials that possess potential advantages over conventional inorganic nanomaterials and organic compounds such as chemical versatility, easy processability, high specific area, low toxicity, biodegradability and electronic and magnetic functionalities to name a few. In this manner, the wise integration of Au nanoparticles with coordination polymers in different types of nanostructures has allowed extending the scope of properties and applications of these systems, allowing also overcoming some of the limitations of Au nanoparticles for certain applications. Therefore, in this review, we discuss the different reported hybrid nanostructures based on the integration of colloidal Au nanoparticles with coordination polymers exhibiting either physical properties of interest (e.g. ferromagnetism, photo-magnetism, spin switching, etc.) or chemical properties (e.g. electrocatalysis). We have paid particular attention to the enhanced properties and the synergistic effects that can emerge from this association. Along this front, thanks to their improved and/or novel properties, these hybrid materials have become promising nanostructures for several applications, especially in biomedicine, catalysis, magnetism and sensing

Decoherence from dipolar interspin interactions in molecular spin qubits

The realization of spin-based logical gates crucially depends on magnetically coupled spin qubits. Thus, understanding decoherence when spin qubits are in close proximity will become a roadblock to overcome. Herein, we propose a method free of fitting parameters to evaluate the qubit phase memory time Tm in samples with high electron spin concentrations. The method is based on a model aimed to estimate magnetic nuclear decoherence [P. C. E. Stamp and I. S. Tupitsyn, Phys. Rev. B 69, 014401 (2004)]. It is applied to a ground-spin J=8 magnetic molecule 1 displaying atomic clock transitions, namely [HoIII(W5O18)2]9−, which remarkably increase Tm at unusually high electron-spin concentrations. Our approach unveils the causes that limit the coherence reached at the clock transitions in challenging systems such as 1, where recent models fail

Air stable hybrid organic-inorganic light emitting diodes uzing ZnO as the cathode

An air stable hybrid organic-inorganic light emitting device is presented. This architecture makes use of metal oxides as charge injecting materials into the light emitting polymer, avoiding the use of air sensitive cathodes commonly employed in organic light emitting diode manufacturing. We report the application of zinc oxide as a cathode in an organic light emitting device. This electroluminescent device shows high brightness levels reaching 6500 cd/m2 at voltages as low as 8 V. Compared to a conventional device using low workfunction metal cathodes, our device shows a lower turn-on voltage and it can operate in air

Single-Crystal-to-Single-Crystal Anion Exchange in a Gadolium MOF: Incorporation of POMs and [AuCl4]−

The encapsulation of functional molecules inside porous coordination polymers (also known as metal-organic frameworks, MOFs) has become of great interest in recent years at the field of multifunctional materials. In this article, we present a study of the effects of size and charge in the anion exchange process of a Gd based MOF, involving molecular species like polyoxometalates (POMs), and [AuCl4]−. This post-synthetic modification has been characterized by IR, EDAX, and single crystal diffraction, which have provided unequivocal evidence of the location of the anion molecules in the framework

Molecular spins for quantum computation

Spins in solids or in molecules possess discrete energy levels, and the associated quantum states can be tuned and coherently manipulated by means of external electromagnetic fields. Spins therefore provide one of the simplest platforms to encode a quantum bit (qubit), the elementary unit of future quantum computers. Performing any useful computation demands much more than realizing a robust qubit¿one also needs a large number of qubits and a reliable manner with which to integrate them into a complex circuitry that can store and process information and implement quantum algorithms. This 'scalability' is arguably one of the challenges for which a chemistry-based bottom-up approach is best-suited. Molecules, being much more versatile than atoms, and yet microscopic, are the quantum objects with the highest capacity to form non-trivial ordered states at the nanoscale and to be replicated in large numbers using chemical tools

Modelling the properties of magnetic clusters with complex structures: how symmetry can help us

The purpose of this article is to answer the question of how symmetry helps us to investigate and understand the properties of nanoscopic magnetic clusters with complex structures. The systems of choice will be the three types of polyoxometalates (POMs): (1) POMs containing localised spins; (2) reduced mixed-valence (MV) POMs; (3) partially delocalised POMs in which localised and delocalised subunits coexist and interact. The theoretical tools based on various kinds of symmetry are the following: (1) irreducible tensor operator (ITO) approach based on the so-called 'spin-symmetry' and MAGPACK program; (2) group-theoretical assignment of the exchange multiplets based on spin- and point symmetries; (3) group-theoretical classification of the delocalised electronic and electron-vibrational states of MV POMs; (4) general approach (based on spin symmetry) to evaluate the energy levels of large MV clusters and the corresponding MVPACK program; (5) computational approach (employing point symmetry) to solve multidimensional non-adiabatic vibronic problems in the nanoscopic systems realized as VIBPACK software. We made it our goal to avoid a conventional deductive style of presentation. On the contrary, we first consider specially selected complex POMs and then show by what methods and in what way the theoretical problems arising in the description of the properties of these molecules can be properly solved

Insights on the coupling between vibronically active molecular vibrations and lattice phonons in molecular nanomagnets

Spin-lattice relaxation is a key open problem to understand the spin dynamics of single-molecule magnets and molecular spin qubits. While modelling the coupling between spin states and local vibrations allows to determine the more relevant molecular vibrations for spin relaxation, this is not sufficient to explain how energy is dissipated towards the thermal bath. Herein, we employ a simple and efficient model to examine the coupling of local vibrational modes with long-wavelength longitudinal and transverse phonons in the clock-like spin qubit [Ho(W5O18)2]9−. We find that in crystals of this polyoxometalate the vibrational mode previously found to be vibronically active at low temperature does not couple significantly to lattice phonons. This means that further intramolecular energy transfer via anharmonic vibrations is necessary for spin relaxation in this system. Finally, we discuss implications for the spin-phonon coupling of [Ho(W5O18)2]9− deposited on a MgO (001) substrate, offering a simple methodology that can be extrapolated to estimate the effects on spin relaxation of different surfaces, including 2D materials

Fe(II) spin crossover complexes of a derivative of 2,6-bis(pyrazol-1-yl)pyridine (1-bpp) functionalized with a carboxylic acid in the 3-pyridyl position

The preparation of a new bis(pyrazol-1-yl)pyridine (1-bpp) derivative functionalized with a carboxylic acid in the 3-pyridyl position, bpp3-COOH ligand is reported together with the structure and spin-crossover (SCO) properties of [FeII(bpp3-COOH)2](ClO4)2·0.5EtOH·0.5H2O (1). Magnetic properties of 1 indicate that LS is favored. Desolvation leads to a gradual and incomplete SCO. Solvated and desolvated compounds show LIESST effect