Research

Researchers Prof. Eliseo Ruiz Magnetic molecules for electronic devices is the main part of the emerging research field known as Spintronics. In order to build up such devices, the molecules are deposited on metallic surfaces to have a monolayer. Thus, the molecules are easily accessible to a second electrode, for instance the tip of an STM microscope or also to build devices using fixed-electrodes breakjunction techniques. These magnetic properties can also be calculated and also the conductance through magnetic molecules using DFT methods combined with non-equilibrium Green Functions. In our group, we are using Green function methods to study the transport properties and simultaneously performing STM experiments to measure the conductance at the single-molecule level. Relevant Publications A. C. Aragonès, D. Aravena, F. J. Valverde-Muñoz, J. A. Real, F. Sanz, I. Díez-Pérez and E. Ruiz. «Metal-Controlled Magnetoresistance at Room Temperature in Single-Molecule Devices». J. Am. Chem. Soc., 2017, 139, 5768-5778. E. Burzuri, J. O. Island, R. Díaz-Torres, A. Fursina, A. González-Campo, O. Roubeau, S. J. Teat, N. Aliaga-Alcalde, E. Ruiz and H. S. J. van der Zant. «Sequential Electron Transport and Vibrational Excitations in an Organic Molecule Coupled to Few-Layer Graphene Electrodes.» ACS Nano, 2016, 10, 2521-2527. J. Ponce, C. R. Arroyo, S. Tatay, R. Frisenda, P. Gaviña, D. Aravena, E. Ruiz, H. J. van der Zant, E. Coronado, «Effect of Metal Complexation on the Conductance of Single-Molecular Wires Measured at Room Temperature», J. Am. Chem. Soc. 2014, 136, 8314-8322. E. Ruiz. «Charge transport properties of spin crossover systems», Phys.Chem.Chem.Phys. 2014, 16, 14. G. Magadur, J.-S. Lauret, G. Charron, F. Bouanis, E. Norman, V. Huc, C.-S. Cojocaru, S. Gómez-Coca, E. Ruiz, T. Mallah, «Charge Transfer and Tunable Ambipolar Effect Induced by Assembly of Cu(II) Binuclear Complexes on Carbon Nanotube Field Effect Transistor Devices», J. Am. Chem. Soc. 2012, 134, 7896-7901. D. Aravena, E. Ruiz, «Coherent transport through spin-croosover single molecules», J. Am. Chem. Soc. 2012, 134, 777-779. E. Ruiz, F. Nunzi and S. Alvarez, «Magnetic communication through functionalized nanotubes: A theoretical study», Nano Letters 2006, 6, 380-384.

Researchers Prof. Santiago Alvarez, Dr. Gabriel Aullón Our research on stereochemistry, bonding and reactivity deals mostly with transition metals, dealing with the geometric factors that affect multiple metal-metal bond strength, or delocalized bonding in M2X2 diamonds, M3X2 and M2X3cages.  The study of the relationship between stereochemistry and spin state has led us to formulate simple rules to predict the geometries of four and six-coordinated transition metals. We are also concerned about intermolecular bonding, from d10···d10metallophilic interactions to homopolar dihydrogen bonding in dimers of simple alkanes and polyhedranes.  Using continuous shape measures methodology, we have also contributed to precise stereochemical description of metal complexes with ill-defined coordination numbers due to the weak coordination of one or more ligands.  Also comprehensive structural analysis of non bonded intermolecular distances in crystal structures has allowed us fo propose a cartography of the Van der Waals territory and a new set of Van der Waals radii.  Related studies have also resulted in a proposal of an coordination ability index for a wide number of anions and solvents. Main Results of Our Research in this Field Data Available for Download: Relevant Publications S. Alvarez, E. Ruiz.  «Self-Assembly of Coordination Compounds: Design Principles», in Supramolecular Chemistry, From Molecules to Nanomaterials, J. W. Steed, P. A. Gale, eds., John Wiley & Sons, Chichester, UK, 2012, 5, 1993-2044.  ISBN 978-0-470-74640-0 E. Ruiz, J. Cirera and S. Alvarez, «Spin density distribution in transition metal complexes», Coord. Chem. Rev. 2005, 249, 2649-2660. S. Alvarez, «Bonding and stereochemistry of three-coordinated transition metal compounds», Coord. Chem. Rev. 1999, 193-5, 13-41. All Publications of Stereochemistry, Bonding and Reactivity of Transition Metal Compounds.  

Researchers Prof. Santiago Alvarez, Prof. Pere Alemany, Prof. Miquel Llunell Continuous symmetry measures (CSM), continuous chirality measures (CCM) and continuous shape measures (CShM) provide simple and accurate stereochemical descriptors for molecular structures.  Derived tools, such as shape maps, minimal distortion paths, and generalized polyhedral interconversion coordinates have been developed in our research group.  Their application to large structural data sets has allowed us to redefine the qualitative rules that govern the stereochemical preferences of four- and six-coordinate complexes. For some stereochemical problems one needs a better description of molecular shape and symmetry than that given by the atomic positions.  To fulfill that need we have proposed an extension of the CSM approach to analyze chemical bonding in terms of the symmetry contents of the electron density, the Hamiltonian or of individual molecular orbitals. Main Results of Our Research in this Field SHAPE 2.1 – Our software for obtaining continuous shape measures of coordination polyhedra and derived properties is available for download. Relevant Publications P. Alemany, D. Casanova, S. Alvarez, C. Dryzun and D. Avnir.  «Continuous Symmetry Measures: A New Tool in Quantum Chemistry».  Rev. Comput. Chem., 2017, 30, 289-352. S. Alvarez, «Distortion Pathways of Transition Metal Coordination Polyhedra Induced by Chelating Topology».  Chem. Rev., 2015, 115, 13447-13483.  Doi: 10.1021/acs.chemrev.5b00537. Open access. L. J. K. Cook, R. Mohammed, G. Sherborne, S. Alvarez and M. Halcrow, “Spin-state Behaviour of Iron(II)Dipyrazolylpyridine Complexes. New Insights from Crystallographic and Solution Measurements». Coord. Chem. Rev., 2015, 289-290, 2-12. Doi: 10.1016/j.ccr.2014.08.006. S. Alvarez, E. Ruiz.  «Self-Assembly of Coordination Compounds: Design Principles», in Supramolecular Chemistry, From Molecules to Nanomaterials, J. W. Steed, P. A. Gale, eds., John Wiley & Sons, Chichester, UK, 2012, 5, 1993-2044.  ISBN 978-0-470-74640-0 S. Alvarez, J. Echeverría.  «New Perspectives on Polyhedral Molecules and their Crystal Structures».  J. Phys. Org. Chem. 2010, 23, 1080-1087. S. Alvarez.  «Nesting of Fullerenes and Frank-Kasper Polyhedra».  Dalton Trans., 2006, 2045-2051. S. Alvarez, P. Alemany, D. Casanova, J. Cirera, M. Llunell, D. Avnir.  «Shape Maps and Polyhedral Interconversion Paths in Transition Metal Chemistry».  Coord. Chem. Rev.2005, 249, 1693-1708. J. Cirera, E. Ruiz, S. Alvarez.  «Continuous Shape Measures as a Stereochemical Tool in Organometallic Chemistry».  Organometallics 2005, 24, 1556-1562. S. Alvarez, P. Alemany, D. Avnir.  «Continuous Chirality Measures in Transition Metal Chemistry».  Chem. Soc. Rev. 2005, 34, 313-326. S. Alvarez.  «Polyhedra in (Inorganic) Chemistry».  Dalton Trans. 2005, 2209-2233. S. Alvarez.  «Poliedros y sus distorsiones en la descripción de la estructura molecular y en el diseño de edificios supramoleculares».  An. Real Soc. Esp. Quím. 2003, 99, 29-44. All Publications of Continuous Shape and Symmetry Measures. Applications in Structural Chemistry.  

Researchers Prof. Eliseo Ruiz Some polynuclear transition metal complexes, known as single molecule magnets (SMM), show a slow relaxation of the magnetization and, as a result, each individual molecule behaves as a magnet. Hence, SMM’s have been proposed either as potential materials for information storage at the molecular level or as qubits in quantum computers, due to their quantum-controlled spin flip. In this field, the Holy Grail is an SMM with a high enough spin inversion barrier to avoid both the thermal spin flip and quantum tunneling effects. The synthesis of new SMMs is a serendipitous search for large energy barriers (large total spin and large and negative magnetic anisotropy). However, theoretical methods allow us to understand and rationalize the experimental data and to point out new synthetic targets. The use of electronic structure calculations allows to determine all the exchange coupling constants present in the same as well as the magnetic anisotropy that is usually quantified by means of the zero-field splitting parameters. Also, low-spin magnetic molecules have been also proposed as molecular qubits. Our research is focusing on the spin relaxation properties of such systems, in order to extract qualitative predictions about the coherence time of such systems. In our group, we are performing both the theoretical studies and the experimental synthesis and characterization of SMM systems. Relevant Publications M. Ding, G. E. Cutsail III, D. Aravena, D.; M. Amoza, M. Rouzieres, P. Dechambenoit, Y. Losovyj, M. Pink, E. Ruiz, R. Clérac and J. M. Smith. «A low spin manganese(iv) nitride single molecule magnet.» Chem. Sci. 2016, 7, 6132-6140. Doi: 10.1039/C6SC01469K S. Gómez-Coca, E. Cremades, N. Aliaga-Alcalde, E. Ruiz, “Huge Magnetic Anisotropy in a Trigonal-Pyramidal Nickel(II) Complex”, Inorg. Chem. 2014, 53, 676-678. D. Aravena, E. Ruiz. «Shedding Light on the Single-Molecule Magnet Behavior of Mononuclear DyIII Complexes», Inorg. Chem. 2013, 52, 13770-13778. E. Colacio, J. Ruiz, E. Ruiz, E. Cremades, J. Krzystek, S. Carretta, J. Cano, T. Guidi, W. Wernsdorfer, E. K. Brechin. «Slow Magnetic Relaxation in a Co(II)-Y(III) Single-Ion Magnet with Positive Zero-Field Splitting», Angew. Chem. Int. Ed. 2013, 52, 9130-9134. S. Gómez-Coca, E. Cremades, N. Aliaga-Alcalde, E. Ruiz. «Mononuclear Single-Molecules Magnets: Tailoring the Magnetic Anisotropy of First-Row Transition-Metal Complexes», J. Am. Chem. Soc. 2013, 135, 7010-7018. E. Cremades, S. Gomez-Coca, D. Aravena, S. Alvarez, E. Ruiz, “Theoretical Study of Exchange Coupling in 3d-Gd Complexes: Large Magnetocaloric Effect Systems”, J. Am. Chem. Soc. 2012, 134, 10532−10542 J. Cirera, E. Ruiz, S. Alvarez, F. Neese and J. Kortus, «How to Build Molecules with Large Magnetic Anisotropy», Chem. Eur. J. 2009, 15, 4078-4087. E. Ruiz, T. Cauchy, J. Cano, R. Costa, J. Tercero and S. Alvarez, «Magnetic structure of the large-spin Mn10 and Mn19 complexes: A theoretical complement to an experimental milestone», J. Am. Chem. Soc. 2008, 130, 7420-7426. T. Cauchy, E. Ruiz and S. Alvarez, «Magnetostructural correlations in polynuclear complexes: The Fe4 butterflies», J. Am. Chem. Soc. 2006, 128, 15722-15727. E. Ruiz, J. Cano, S. Alvarez and P. Alemany, «Magnetic coupling in end-on azido-bridged transition metal complexes: A density functional study», J. Am. Chem. Soc. 1998, 120, 11122-11129. E. Ruiz, P. Alemany, S. Alvarez and J. Cano, «Toward the prediction of magnetic coupling in molecular systems: Hydroxo- and alkoxo-bridged Cu(II) binuclear complexes», J. Am. Chem. Soc. 1997, 119, 1297-1303. All Publications of Magnetic Properties of Complex Inorganic Systems.