Synthesis of coordination complexes using nitrogenated macrocycles. Magnetic study

Abstract

“In the last decade, S=1/2 systems of Cu (II) complexes and Cu (II) ions in the solid state have been found to exhibit slow magnetic relaxations. With the aim of progressing toward the entanglement of spin states and quantum computing using spin qubits, a greater number of studies on molecule-based spin qubits that exhibit magnetic interactions will be conducted and will be of increasing importance from now on.” (2) Nickel (II), similarly to copper (II), is a transition metal cation that can show interesting magnetic behaviour when is coordinated with suitable ligands. With an electronic configuration of d8, Ni (II) tends to form stable octahedral geometries, where the presence of unpaired electrons contributes to the magnetic susceptibility of the complex. In polynuclear systems, Ni (II) allows the study of magnetic interactions such as antiferromagnetism, especially when metal centres are connected through bridging ligands like oxalate. Also, its smaller contribution to the Jahn-Teller effect compared to Cu (II) usually results in less distorted structures, which makes the structural and magnetic analysis easier to interpret. (3) This project is focused on the synthesis of new coordination compounds using copper (II) and nickel (II) salts with nitrogenated macrocycles as ligands, combined with oxalate or benzoquinone bridges. The main objective is to create and study these complexes for their potential magnetic properties, with possible future applications in molecular magnets or quantum technologies. During the project, six different compounds were successfully synthesised and characterized. The ligands used (232-N4 and 323-N4) helped to build coordination structures with varying geometries. Techniques like IR spectroscopy and X-ray diffraction were used to analyse their structures. In parallel, their magnetic behaviour was studied using SQUID magnetometry, which allowed precise measurements of magnetization and magnetic susceptibility. Additionally, Electron Paramagnetic Resonance (EPR) was carried out. The complexes showed interesting structural details and magnetic patterns depending on their composition. Concepts such as magnetization, susceptibility, and anisotropy of the g-factor are essential to interpret the results correctly. Through these analyses, it is possible to relate geometric features of the complexes with their magnetic responses, which is a key aspect in the field of molecular magnetism. Although some reactions didn’t give products (which are in the appendix 1), the project contributed valuable knowledge. It supports basic research in coordination chemistry and molecular magnetism, which can be useful in high-density data storage, quantum computing, or advanced sensors in the future