Theoretical and computational studies of magnetic anisotropy and exchange coupling in molecular systems

Abstract

The field of molecular magnetism studies the magnetic properties of molecular systems as opposed to conventional metal-based magnets. The high chemical modifiability of the constituting molecules makes such materials highly versatile, and the small size of the building blocks leads to the rise of various quantum mechanical phenomena, such as tunneling and entanglement. These phenomena can then be further utilized in the construction of nanoscale quantum devices. This dissertation describes computational and theoretical studies in the field of molecular magnetism using state-of-the-art quantum chemical methods based on ab initio multireference approaches and broken symmetry density functional theory. Of the eight papers included in this work, the first three describe the ex- perimental and computational characterization of magnetic interactions between organic radicals, transition metal ions, and lanthanide ions. The next paper introduces an approach to design ferromagnetically coupled organic radical dimers, which can be used in the construction of magnets consisting of purely organic molecules. This theory can also be extended to the design of organo-main-group radical systems and ferromagnetically coupled metal–radical complexes. The following three papers focus on the study of magnetic anisotropy in mono- and polymetallic Dy(iii) coordination complexes. The last paper develops a theoretical model for the description of anisotropic spin-dependent delocalization and applies this model to study the magnetic interactions in excited states of bilanthanide endohedral metallo-fullerenes. In all cases where computational tools are applied to experimentally characterized systems, the computations offer more insight into the electronic structure and chemical properties of the systems, giving rise to the various macroscopically observed magnetic phenomena than what could be obtained by experimental tools only. The results contribute to our understanding of magnetically interesting molecular systems and suggest new research directions in the field.