Design and preparation of functional coordination compounds based on poly-β-diketone and polypyrazolyl ligands
- Autores: Ivana Borilovic
- Directores de la Tesis: Guillem Aromi (dir. tes.)
- Lectura: En la Universitat de Barcelona ( España ) en 2018
- Idioma: español
- Tribunal Calificador de la Tesis: Rodolphe Clérac (presid.), Eliseo Ruiz Sabin (secret.), Marco Evangelisti Crespo (voc.)
- Programa de doctorado: Programa de Doctorado en Química Orgánica por la Universidad de Barcelona
- Materias:
- Texto completo no disponible (Saber más ...)
- Resumen
The close relationship between the coordination chemistry and molecular magnetism has been established from the very beginning of the latter. Combining the versatile organic scaffolds and the diverse physico-chemical properties of transition and rare-earth metals, coordination chemistry illuminated the discovery of numerous molecular functional systems, ranging from the bi-stable single molecule magnets (SMMs) and spin crossover (SCO) materials, to the molecular prototypes of quantum bits (qubits) and logic gates (qugates). On the other hand, systematic studies of magnetic properties provided the meaningful insights into the electronic structure of coordination entities, resulting with many magneto-structural correlations and predictable models. Beyond the fundamental findings, successful integration of molecular magnets to surfaces emerged the evolution of nanoscale magnetic devices and the field of molecular spintronics. As a result, novel interest for the molecular systems was triggered since controlled structural variations among the plethora of building blocks could be exploited to tailor the specific functions. In that context, especially appealing has become the pursuit of systems which will allow the controlled manipulation of molecular spins and charges for the information storage and processing.
Combining the judiciously designed bis−β-diketone and polypyrazolyl scaffolds with the crystal field effects on the 3d metal ions, this manuscript exposes different methods of selective preparation of new heterometallic coordination compounds and the subtle modulation of their magnetic properties. Apart from their conventional magneto-structural relevance, special interest has been dedicated to develop the systems which exhibit strong ferromagnetic coupling and slow relaxation of the magnetization, even when incorporating exclusively isotropic metal ions. Moreover, synthetic strategy based on controlled transfer of the ligand asymmetry to its coordination compounds provided several entities which fulfil the necessary requirements to be exploited as the molecular prototypes of universal logic gates in quantum information processing.
Chapter II presented new synthetic strategy of rational preparation of oxo-hydroxido coupled pair of homometallic and heterometallic dimers based on bis−β-diketone ligand H4L1. Two fused phenol-β-diketone coordination pockets provided enough flexibility for selective manipulation of ligand conformation and coordination modes. Particularly, by imposing pair-impair metal-ligand ratio, with large excess of 3d metal ions, controlled assembly of coupled pairs of dimers or monomers was achieved. Moreover, it was shown that only one ligand molecule in the backbone of the structure was enough to impose desired site selectivity which was successfully exploited to generate all possible heterometallic pairs of late 3d metals. Structural analysis of those coordination entities proved that bonding details correlated with the nature of metal ions can be used as a fingerprinting evidence for correct positional assignment of heterometallic topologies. Magnetic studies proved meaningful insight in strength of antiferromagnetic interactions between identical of diverse spin carries, providing some meaningful knowledge to be exploited. Additionally, it was clearly show that [NiCu] dimers from all possible combinations provide best isolated ground state doublet and thus should be exploited as potential qubit candidates. Gathered knowledge from this section inspired the evolution of Chapter III, where novel library of structurally related asymmetric and multidentate bis−β-diketone ligand was designed and exploited in construction of molecular prototypes of multiqubit quantum logic gates. Direct transfer of imposed asymmetry of the ligands to their coordination compounds enabled successful preparation of three new compounds which fulfil the basic requirement of asymmetry and ground state doublet to be considered as molecular prototypes of C-NOT quantum gates of which one represents very first example of a coordination compound which features the triple asymmetry between the component qubits. As one of the highlights of this research line, it was shown how rational ligand design can be exploited to tune the interaction between individual qubits, while control of reaction stoichiometry can provide means of changing their topology. Also, initial steps are undertaken in expanding the coordination chemistry of more complex bis−β-diketone ligand to vanadium(IV) based qubits.
Chapter IV expanded the ligand library to pyrazole derivatives of bis−β-diketone ligands and exposed extensive coordination chemistry of phenolic pyrazole ligand H4L4. Initial idea behind its implementation was to selectively chelate different 3d metals into linear arrays based on their preference towards (-N,N) or (-O,N) coordination environment of the ligand. Homometallic series of obtained compounds indicated that only vanadyl cation (VO2+) and Mn3+ ion discriminate two different ligating donor sets and reside exclusively in the (-O,N) coordination pocket, leaving central -N4 chelating metal-free, inspired their further use as metalloligands. Great structural rigidity and excessive negative charge of vanadyl metalloligand enhanced its nucleophilic nature, providing means for bitopic structural expansion in selective formation of derived heterobimetallic and heterotrimetallic clusters. Additionally, orthogonality in expansion of metalloligand structure ensured double orthogonality between magnetic orbitals of vanadyl and heavier 3d ions resulting with purely ferromagnetically coupled clusters which even exhibit slow relaxation of magnetization when constructed from isotropic metal ions. Overall, work presented in this thesis exposed different ways of constructing heterometallic compounds providing good initial playground for many novel directions of research within molecular magnetism.
