We report a theoretical evaluation of the properties of iron and titanium impurities in sapphire (corundum structured alpha-Al2O3). Calculations using analytical force fields have been performed on the defect structure with the metals present in isolated, co-doped and tri-cluster configurations. Crystal field parameters have been calculated with good agreement to available experimental data. When titanium and iron are present in neighbouring face and edge-sharing orientations, the overlap of the d-orbitals facilitates an intervalence charge transfer (Fe-III/Ti-III -> Fe-II/Ti-IV) with an associated optical excitation energy of 1.85 eV and 1.76 eV in the respective configurations. Electronic structure calculations based on density functional theory confirm that Fe-III/Ti-III is the ground-state configuration for the nearest-neighbour pairs, in contrast to the often considered Fe-II/Ti-IV pair. Homonuclear intervalence charge transfer energies between both Fe-III/Fe-II and Ti-IV/Ti-III species have also been calculated, with the energy lying in the infra-red region. Investigation of multiple tri-clusters of iron and titanium identified one stable configuration, Ti-III-(Ti-IV/Fe-II), with the energy of electron transfer remaining unchanged.