Crystal Field Theory (CFT) was developed by physicists Hans Bethe and John Hasbrouck van Vleck in the 1930s. CFT describes the interaction between d orbital electrons of a transition metal with the electrons of ligands that are coming together to form coordination complexes. The d orbital electrons act in a unique way by either gaining or losing energy when repulsed by an oncoming electron from a ligand. CFT theory provides an explanation for this energy difference in the d orbital and thereby successfully accounts for some magnetic properties, colors, hydration enthalpies, and spinel structures of transition metal complexes. CFT was subsequently combined with molecular orbital theory to form the more realistic and complex ligand field theory (LFT), which delivers insight into the process of chemical bonding in transition metal complexes.
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