Functional materials, in particular those that display spin crossover (SCO), single molecule magnetism (SMM) and porosity are of increasing interest due to their potential application in spintronic devices and gas storage and separation materials. To further investigate these classes of materials, a variety of Fe(II), Fe(III) and Co(II) complexes have been synthesised featuring pyridylhydrazone and imidazolylimine ditopic ligands. These two families of ligands were selected due to their applicability to Fe(II) and Fe(III) SCO. However, during the course of this work it was uncovered that they were also suitable for the synthesis of molecular porous materials (MPMs) and Co(II) SMMs. Structural characterisation of all complexes was carried out by single crystal X-ray diffraction, accompanied by NMR, ESI-MS, IR, TGA and elemental analysis where appropriate. The SCO properties were analysed in the solid state via variable temperature magnetic susceptibility and absolute reflectivity measurements. Preliminary photomagnetic measurements were conducted on one complex to investigate the presence of Light Induced Excited Spin-State Trapping (LIESST) behaviour. Magnetic anisotropy of Co(II) complexes was indicated via DC magnetic susceptibility measurements and therefore AC magnetic susceptibility measurements were conducted to investigate the slow relaxation of the magnetic moment. The stability of potentially porous materials was first assessed by powder X-ray diffractions while the porosity was verified by gas sorption measurements. The first part of the work detailed in this thesis focuses on the dinuclear helicates, mesocates and tetranuclear grid complexes formed with Fe(II), Fe(III) and Co(II) with ditopic pyridylhydrazone ligands. Particular attention was paid to their intramolecular interactions and crystal packing. Where appropriate, the SCO and porosity were investigated using the techniques outlined above. The second part of this work focuses on the use of ditopic imidazolylimine ligands for the synthesis of Fe(II) SCO helicates. The variation of the peripheral imidazole functionality, the anion and crystallisation conditions had a significant impact on the crystal packing and therefore the SCO properties. Preliminary investigation were carried out using Co(II) in the place of Fe(II) for the synthesis of SMM helicates and synthesising Fe(II) SCO helicates featuring mesogenic substituents. The latter was analysed via DSC and SAXS to investigate the occurrence of a phase change associated with the formation with a mesogenic phase.