Multistep spin-crossover in Hofmann frameworks containing functionalised ligands

This thesis focuses on the design, synthesis and characterisation of 2-D and 3-D Hofmann-like spin crossover (SCO) frameworks that incorporate functionalised 1,2,4-triazole or pyridine ligands. The overall aim is to strategically induce structural distortion through the inclusion of ligand functional groups with competing supramolecular interactions and explore the consequence to Hofmann structural and SCO properties. By this approach, this thesis is intended to contribute to enabling a deeper understanding of the structural drivers of diverse SCO characters, in particular multistep SCO profiles. This thesis is divided into two parts. In Part I (Chapters 3-5), a family of 2-D Hofmann-type frameworks are presented that include 1,2,4-triazole ligands functionalised to explore the impact of ligand length and supramolecular interaction capacity (including hydrogen bonding and -stacking) on the structure and SCO properties. In Part II (Chapters 6-7), 2-D and 3-D Hofmann-type frameworks are presented which include pyridyl ligands functionalised to study the effect of ligand length, steric bulk, and supramolecular interaction capacity (including hydrogen bonding and -stacking) on the structure and SCO properties. All of the materials presented in this thesis show notable structural distortion and undergo thermally induced SCO transitions, including many cases of multistep SCO character. Structure-function relationships are explored across all of the materials presented using a range of variable temperature structural and physical measurements. In Chapter 3, other SCO perturbations are explored, including, light-induced SCO, pressure-induced SCO and/or guest-modified SCO.Part I: Hofmann frameworks containing functionalised 1,2,4-triazole ligandsChapter 3 presents the 2-D Hofmann-type framework [Fe(cintrz)2Pd(CN)4]∙guest, where cintrz = (1E,2E)-3-phenyl-N-(4H-1,2,4-triazol-4-yl)prop-2-en-1-imine and guest = 3H2O, 2H2O, ∅. The framework shows structural distortion away from