Controlled heterometallic composition in linear trinuclear [LnCeLn] lanthanide molecular assemblies

The combination of two different β-diketone ligands facilitates the size-controlled assembly of pure heterometallic [LnLn′Ln] linear compounds thanks to two different coordination sites present in the molecular scaffold. [HoCeHo], [ErCeEr], and [YbCeYb] analogues are presented here and are characterized both in the solid state and in solution, demonstrating the selectivity of this unique method to produce heterometallic 4f molecular entitie

A Dissymmetric [Gd2] Coordination Molecular Dimer Hosting six Addressable Spin Qubits

Artificial magnetic molecules can host several spin qubits, which could then implement small-scale algorithms. In order to become of practical use, such molecular spin processors need to increase the available computational space and warrant universal operations. Here, we design, synthesize and fully characterize dissymetric molecular dimers hosting either one or two Gadolinium(III) ions. The strong sensitivity of Gadolinium magnetic anisotropy to its local coordination gives rise to different zero-field splittings at each metal site. As a result, the [LaGd] and [GdLu] complexes provide realizations of distinct spin qudits with eight unequally spaced levels. In the [Gd2] dimer, these properties are combined with a Gd-Gd magnetic interaction, sufficiently strong to lift all level degeneracies, yet sufficiently weak to keep all levels within an experimentally accessible energy window. The spin Hamiltonian of this dimer allows a complete set of operations to act as a 64-dimensional all-electron spin qudit, or, equivalently, as six addressable qubits. Electron paramagnetic resonance experiments show that resonant transitions between different spin states can be coherently controlled, with coherence times TM of the order of 1 µs limited by hyperfine interactions. Coordination complexes with embedded quantum functionalities are promising building blocks for quantum computation and simulation hybrid platforms

Thermodynamic stability of heterodimetallic [LnLn] complexes: synthesis and DFT studies

The solid-state and solution configurations of the heterodimetallic complexes (Hpy)[LaEr(HL)(3)(NO3)(py)(H2O)] (1), (Hpy)[CeEr(HL)(3)(NO3)(py)(H2O)] (2), (Hpy)[CeGd(HL)(3)(NO3)(py)(H2O)] (3), (Hpy)[PrSm(HL)(3)(NO3)(py)(H2O)] (4), and (Hpy)(2)[LaYb(HL)(3)(NO3)(H2O)](NO3) (5), in which H3L is 6-(3-oxo-3-(2-hydroxyphenyl)propionyl)pyridine-2-carboxylic acid and py is pyridine, were analyzed experimentally and by using DFT calculations. Complexes 3, 4, and 5 are described here for the first time, and were analyzed by using single-crystal X-ray diffraction and mass spectrometry. The theoretical study was also extended to the [LaCe] and [LaLu] analogues. The results are consistent with a remarkable selectivity of the metal distribution within the molecule in the solid state, enhanced by the size difference between the different ions. This selectivity was reduced in solution, particularly for ions with the most similar radii. This unique entry into 4f-4f heterometallic chemistry establishes for the first time the difference between the selectivity in solution and that in the solid state, as a result of changes to the coordination that follow the dissociation of terminal ligands upon dissolution of the complexes

Diseño de ligandos β-dicetona y sus agregados metálicos funcionales: estudio cristalográfico y magnético

[spa] Desde hace años la ciencia del magnetismo ha centrado uno de sus objetivos más ambiciosos en el estudio y creación de dispositivos funcionales a escala molecular. Un ejemplo es el intento de implementación de la computación cuántica mediante el espín molecular. En este contexto, un objetivo es utilizar agregados metálicos como bits cuánticos. Con esta finalidad se ha estructurado el trabajo de esta tesis en cuatro bloques, con el fin de sintetizar moléculas que contengas clústeres magnéticos, los cuales contengan espines bien definidos, en estados diferenciados y que mantengan una ligera interacción y un tiempo de coherencia largo, con tal de cumplir con los requisitos para el procesado de puertas lógicas. Los cuatro bloques se dividen en: A) Elección, diseño, síntesis y caracterización de los ligandos orgánicos, precursores para la los componentes del ensamblaje molecular. Todos ellos basados en la combinación de grupos dipicolinato y grupos β-dicetona que favorezcan la coordinación y añadan propiedades a los ligandos para facilitar la cristalización. Finalmente se obtienen cinco nuevos ligandos, los cuales aportan una coordinación asimétrica para los centros metálicos. Al diferenciar entre sus entornos de coordinación, permite sintetizar compuestos heterometálicos en reacciones de una sola etapa, incluso para cationes de la serie lantánida. B) Síntesis de agregados hetero-dinucleares de lantánidos. En este apartado se procede al estudio sistemático de un gran número de estructuras nuevas del tipo [LnLn’(HL1)2(H2L1)(py)(NO3)(H2O)] cuyo análisis arroja información muy interesante. La caracterización se fundamenta en el conocimiento de su estructura cristalina mediante la difracción de rayos-X de monocristal y la pureza y selectividad del sistema a través de análisis convencionales y la fragmentación isotópica a través de la espectrometría de masas. De esta forma durante el análisis cristalográfico se puede observar el efecto de la contracción lantánida al estudiar los parámetros concernientes a los metales y las distancias de enlace respecto al radio atómico de estos. También se estudia la capacidad para aislar sistemas heterometálicos puros, que se mantiene para un gran número de combinaciones pero disminuye cuando la diferencia de radio atómico entre ambos metales se vuelve muy pequeña, y es menos eficiente si nos desplazamos hacia metales más pesados. Para confirmar dichos resultados también se realizan varios cálculos DFT que arrojan evidencias de la estabilidad termodinámica del sistema en una única distribución posicional. Varios de estos compuestos se emplean para el estudio de sus aplicaciones funcionales. Así el sistema de [Dy2] se perfila como un potencial candidato para la realización de puertas lógicas, cumpliendo con los requisitos necesarios para tal efecto y manteniéndose efectivo tras su deposición en superficie. También se estudia la fotoluminiscencia del compuesto [LaEu], que se muestra a bajas temperaturas y con un tiempo de vida medio relativamente corto a causa, principalmente, del poco eficiente efecto antena del ligando. C) Mediante esquemas de reacción similares a la anterior y siguiendo principios análogos se preparan agregados para la explotación de las propiedades del bloque-f y el incremento de la complejidad estructural. Se sintetizan compuestos trinucleares de fórmula [LnLn’2(L3)2(L4)2(H2O)2py]NO3. Los cuales siguen siendo estables en solución y muestran un alto grado de pureza, por tanto, este tipo de síntesis abre grandes posibilidades para la realización de puertas lógicas complejas. D) La síntesis de sales de cobalto en condiciones básicas y en solución de piridina da lugar a dos compuestos puros en forma cristalina. Ambos muestran características estructurales excepcionales. Además uno de ellos, a través de una reacción aeróbica es capaz de atrapar moléculas de CO2 en su interior.[eng] In order to synthesize molecules containing magnetic clusters and employ their molecular spins as quantum bits which they can fulfil the requirements for processing logic gates this thesis work has been structured in four blocks. A) Selection, design, synthesis and characterization of organic ligands, precursors for molecular assembly components. They are based on the β-diketone groups and other functional groups which promote the coordination. New ligands are obtained, which provide an asymmetric coordination to the metal centers. Differentiating between their coordination environments, they synthesize heterometallic compounds in a single step reaction, even for the lanthanide series cations. B) Synthesis of aggregates hetero-dinuclear lanthanide. It was proceed to the systematic study of a large number of new structures type [LnLn'(HL1)2(H2L1)(py)(NO3)(H2O)]. The characterization is based on the knowledge of its crystal structure, and the purity by isotopic fragmentation through mass spectrometry. During the crystallographic analysis was observed the effect of the lanthanide contraction during the study of the parameters concerning metals and bond distances with respect to atomic radius of these. It studied the ability to isolate pure heterometallic systems. DFT calculations yield evidence of the thermodynamic stability of the system in a single positional distribution. The system [Dy2] emerged as a potential candidate for the realization of logic gates, achieving the requirements for this purpose. Photoluminescence of the compound [LaEu] showed at low temperatures a short half life time because of inefficient antenna effect of the ligand. C) By similar reaction schemes was prepared aggregates with greater structural complexity. Trinuclear compounds of formula [LnLn'2(L3)2(L4)2(H2O)2py]NO3 are synthesized. They remained stable in solution and showed a high degree of purity, therefore, open up great possibilities for the realization of complex logic gates. D) Synthesis with cobalt salts under basic conditions and in pyridine solution results in two pure compounds in crystalline form. Both showed exceptional structural characteristics. Furthermore, one of them, through an aerobic reaction was able to trap molecules of CO2

Catalytic H-2 Evolution with CoO, Co(OH)(2) and CoO(OH) Nanoparticles Generated from a Molecular Polynuclear Co Complex

Electrochemical water reduction by employing first-row transition-metal nanoparticles (NPs) constitutes a sustainable way for the generation of H-2. We have synthesized Co-based NPs from a molecular Co-II/Co-III precursor after its reductive decomposition at -1.86 V versus NHE in different organic solvents. These NPs are able to electrochemically reduce water at pH 14. SEM, EDX and XPS analyses have allowed the determination of the chemical nature of the as-deposited NPs: CoO when using MeCN as the solvent and CoO(OH) when employing either dichloromethane (DCM) or MeOH. After 2 h of constant polarization at 10 mAcm(-2), the electrocatalytic activity of the NPs obtained in MeCN and DCM decreases, whereas it increases for those obtained in MeOH. In this solvent, the overpotential is reduced by 215-220 mV and the specific current density is tripled. Interestingly, during this activation process in MeOH, the precursor CoO(OH) NPs are converted into Co(OH)(2). The implications of these results in the context of the current research in the field are also discussed