Furthermore, computational approaches must explicitly define the species involved, a requirement which can be challenging and even misleading when the precise speciation is unknown due to lack of experimental studies. While the speciation of Ni(II) in the presence of bipyridine type ligands has been studied rigorously, the results are fairly complicated (i.e. slow equilibrium formation of a mixture of species with 0, 1, 2, or 3 bipyridine ligand molecules bound to Ni), and the speciation is expected to vary depending on the particular reaction conditions (e.g. solvent, Ni:ligand molar ratio, ligand identity, and the presence of other reaction components that may ligate Ni). As a result, data concerning the reactivity of specific Ni-bipyridine complexes in dual Ni photocatalysis is severely limited.