Ligand to metal charge transfer transitions LMCT

Ligand-to-metal charge transfer (LMCT) transitions between the bonding ligand-centred MOs and antibonding metal-centred MOs. Such transitions are found where a ligand is easily oxidised and the metal is easily reduced. 

The lowest transition energies of permanganate and dichromate will be ligand to metal charge transfer (LMCT) in nature. From symmetry arguments, it can be shown that the transition described by the 4—> e one-electron transition of a tetrahedral d° complex will have an Aj/Dj ratio of -0.5 (108,109). 

Figure 11.4 Energy level diagram for an octahedral transition metal complex showing the various kinds of electronic transition. MC = metal-centred, LC = ligand-centred, MLCT = metal-to-ligand charge transfer, LMCT = ligand-to metal-charge transfer.

Fig. 1. Schematic orbital energy diagram representing various types of electronic transitions in octahedral complexes. A line connects an atomic orbital to that molecular orbital in which it has the greatest participation. 1 metal centered (MC) transitions 2 ligand centered (LC) transitions 3a ligand-to-metal charge transfer (LMCT) transitions 3b metal-to-ligand charge transfer (MLCT) transitions...

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