Estudio de diferentes estrategias para la síntesis de compuestos de oro(I) con propiedades luminiscentes de alta eficiencia stars

Abstract

Gold(I) complexes bearing P- and N-ligands constitute a very interesting class of molecular materials as they can give rise to novel structural and photophysical properties due to their great coordinative versatility. The properties of these compounds can be modulated depending on the type of ligand used, being of special interest those with a high structural rigidity. Thus, the presence of a rigid structure in the complexes makes non-radiative processes unfavourable, which results in the presence of high efficiency emissions. In this context, the present work is devoted to obtain high efficiency luminescent compounds based on the synthesis, spectroscopic characterisation, structural description and study of the photophysical properties, as well as their computational interpretation, of new systems based on gold(I) complexes with different phosphine (P-donor) or pyridine (N-donor) ligands. First, Au(I) compounds with different coordination environments have been prepared using in the synthesis different gold(I) precursors and a diphosphine ligand able to act as a bi- or monodentate ligand. Thus, organometallic compounds have been obtained in which the ligand acts as a chelate and the gold(I) centres are tetracoordinated, complexes in which the ligand acts as a bridge giving rise to dinuclear compounds or, alternatively, in which act as a monodentate ligand generating mononuclear dicoordinated species. All these compounds show interesting and varied photoluminescent properties directly related to their structural properties. On the other hand, a new family of tricoordinated gold(I) compounds based on di- and tetraphosphine ligands has been designed. The P-donor ligands used are rigid ligands that act as electron density acceptors in charge transfer processes, responsible for the luminescent properties of the complexes. With respect to the gold(I) centres, they are attached to different perhalophenyl groups, which, although a priori seem to be innocent ligands with respect to the photophysical properties of the complexes, experimental data and computational studies reveal a key and not so evident role in them. Thus, by making modifications to the molecular fragments involved in the electronic transitions responsible for the emissive properties, a direct impact on the wavelength tuning is observed. Interestingly, the photophysical properties of this type of compounds have allowed us to carry out an in-depth study of a very interesting and underexplored radiative phenomenon for gold(I) centres, called Thermally Activated Delayed Fluorescence (TADF). Finally, in order to explore how the presence of other metal centres affects more rigid matrices such as gold(I) metallopolymers based on the organic polymer poly(4-vinylpyridine), silver(I) metal centres have been incorporated into these systems in different Au(I):Ag(I) ratios. Thus, heterometalopolymers have been obtained, in which the gold(I) and silver(I) metal centres are coordinated to N-donor groups, showing espectacular luminescent properties. Thus, the emission energies show a strong dependence on the stoichiometric Au(I):Ag(I) ratio, on the excitation energies and on the temperature. Within this line of research focused on the use of rigid matrices, a study based on the incorporation of discrete linear gold(I) compounds with N-dador ligands into polymeric matrices has been started. This new strategy allows changes in the rigidity of the derivatives and, consequently, an increase in the emission efficiency of the complexes due to an increase in their quantum yield.