Exploiting the Potential of New Coordination Frameworks for Technological Applications – from Temperature Sensing to Magnetic Storage

This PhD work reports on the design, synthesis and characterization of novel Coordination Frameworks (CFs), either porous or not, showing magnetic and/or optical properties, to exploit their potential in various technological applications. The design of such materials requires a particular attention in the selection of the molecular building blocks, organic linkers and metal nodes. To construct CFs with different physical properties, carboxylate and anilate derivatives have been chosen. Particularly, among the carboxylates, the 1,3,5-benzentricarboxylic acid (H3BTC, trimesic acid), a biofriendly linker which allows to build robust 3D metal-organic frameworks while within the anilates, the 3,6-ditriazolyl-2,5-dihydroxybenzoquinone was chosen for its potential capability to build 3D supramolecular architectures due to the triazolyl pendant arms at the 3, 6 positions of the benzoquinone moiety, which are electron-donor substituents as well; these substituents in fact may affect the physical properties and the related technological applications. By playing with these two promising linkers in a wise combination with selected d- and f- transition metals, new systems, suitable for a wide range of applications, were obtained. In Chapter 1, the synthesis of two N-heterocycles substituted anilate derivatives, 3,6-N-ditriazolyl-2,5-dihydroxy-1,4-benzoquinone and 3,6-N-(dipyrazolyl-4-carboxylic acid)-2,5-dihydroxy-1,4-benzoquinone, is reported. Both ligands were characterized by spectroscopic (Raman, FT-IR, UV-Vis and Fluorescence) and electrochemical (Cyclic Voltammetry) techniques. Chapter 2 reports on the synthesis of new magnetic and redox-active anilate-based 3D MOFs, obtained by combining the 3,6-N-ditriazolyl-2,5-dihydroxy-1,4-benzoquinone, hereafter 3,6-N-ditriazolyl-Anilato, linker with MII= Co, Cu, Mn, Ni and Fe d-transition metal ions. Structural, Spectroscopic, Magnetic and Electrochemical Characterization is reported for all the obtained materials. In Chapter 3, the CoII-3,6-N-ditriazolyl-Anilato 3D MOF was studied as potential system for CO2 uptake and separation. The static and dynamic adsorption studies revealed that this MOF present a remarkable CO2 adsorption and separation capability from gas mixtures, due to its 3D ultramicroporous structure, with voids X where the N2 atoms of the triazolyl groups show a significant affinity for CO2 molecules and channels that enable the high selective entrance of CO2. Chapter 4 reports on the synthesis of novel flexible 3D Er-based MOF with the 3,6-N-ditriazolyl-Anilato linker, showing luminescent and SIM properties. These materials have been structurally, magnetically and optically characterized. Furthermore, one of them shows a reversible structural flexibility of the 3D framework that allows a challenging tuning of its physical properties. In Chapter 5, the potential of 3,6-N-ditriazolyl-2,5-dihydroxy-1,4-benzoquinone as organic linker for LnIII ions was exploited by combining it with DyIII, TbIII and HoIII ions, which are generally employed as building units for Single Ion Magnets (SIMs). As in the previous Chapter, two series with all the LnIII ions were obtained and further characterized, both structurally and magnetically. Finally, Chapter 6 reports on the preparation through a solvent-free synthesis of YbIII/NdIII mixed CFs, in different stoichiometric ratios, by using 1,3,5-benzentricarboxylic acid (H3BTC) as biofriendly organic linker, for biomedical applications as ratiometric thermometers in the physiological temperature range (298-313 k). The materials were structurally and morphologically characterized through XRD and SEM, while their photophysics was studied at room temperature and at variable temperature, in the 10-300 K range, to test their best performances as thermometers.

This PhD work reports on the design, synthesis and characterization of new Coordination Frameworks (CFs), either porous or not, showing magnetic and/or optical properties, to exploit their potential in various technological applications. Particularly, in Chapter 1, the synthesis and characterization of two N-heterocycles substituted anilates, H2trz2An and 3,6-N-(dipyrazolyl-4-carboxylic acid)-2,5-dihydroxy-1,4-benzoquinone, is reported. Then, Chapter 2 reports on the synthesis and the complete characterization of magnetic and redox-active anilate-based 3D CFs, obtained by combining H2trz2An with MII = Co, Cu, Mn, Ni and Fe. In Chapter 3, the CoII-trz2An 3D MOF was studied as potential system for CO2 uptake and separation. The static and dynamic adsorption studies revealed that this MOF present a remarkable CO2 adsorption and separation capability from gas mixtures, due to its 3D ultramicroporous structure and the N atoms present in the voids. Chapter 4 reports on the synthesis of 3D ErIII-MOF with H2trz2An linker, showing luminescent and Single Ion Magnet (SIM) properties. These materials have been structurally, magnetically and optically characterized. Furthermore, one of them shows a reversible structural flexibility of the 3D framework that allows a tuning of its physical properties. In Chapter 5, H2trz2An was combined with DyIII, TbIII and HoIII ions, typical building units for SIMs, and the two obtained series with all the LnIII ions were structurally and magnetically characterized. Finally, Chapter 6 reports on the preparation via solvent-free synthesis of YbIII/NdIII mixed CFs, in different stoichiometric ratios, by using 1,3,5-benzentricarboxylic acid (H3BTC) as linker, for applications as ratiometric thermometers in a wide temperature range. The materials were structurally and morphologically characterized, while their photophysics was studied at room temperature and at variable temperature (10-300 K), to test their best thermometers performances.