Single-ion magnetism in novel Btp-based cobalt complexes of different charge

The magnetic behavior of single-ion metal complexes may be influenced by the nature and composition of the secondary coordination sphere that can be composed of solvent molecules and counterions bound through non-covalent interactions. However, achieving precise control over the outer-coordination sphere of these magnetic complexes to demonstrate its influence on their magnetic properties presents a challenge. A strategy for varying the number of counterions, while simultaneously preserving the arrangement of the ligand atoms around the metal center without altering its oxidation state, is to adjust the overall formal charge of the complex. This adjustment could lead to changes in the magnetic properties of single-ion metal complexes. In this study, we present two novel ligands featuring the coordinating unit Btp (2,6-bis(1,2,3-triazol-4-yl)pyridine). These ligands are equipped with functional groups that can potentially undergo deprotonation. By carefully selecting the solvents used during the crystallization process of the complexes, we can tune at will the charge of the complexes, thus modifying the composition of the Co^II complexes' outer-coordination sphere. We show that, by modifying these conditions, we can tailor the secondary coordination sphere of both charged (mono- and dicationic) and neutral anisotropic Co^II metal complexes to show field-induced single-ion magnetism, influencing in turn the size of the barrier to reversal of the magnetization and their slow relaxation process.