In relation to d orbital energy, how do they compare with ligand orbitals in a MLCT context?

In a metal-to-ligand charge transfer (MLCT) context, d orbitals of the metal often have energy levels that are influenced by the ligand field created by surrounding ligands. When discussing the comparison of d orbital energy to ligand orbitals, it is essential to understand the nature of the interactions between these orbitals.

In many cases, particularly for metals with d electrons, the energy of the d orbitals can indeed be lower and relatively close to that of the ligand orbitals. This proximity in energy allows for effective electron transfer from the d orbitals to the ligands during the MLCT process. A lower energy d orbital implies that it can participate in bonding interactions with the higher energy ligand orbitals, facilitating the charge transfer that characterizes MLCT.

This closeness in energy is particularly significant as it enhances the likelihood of transitions between these orbitals when the system is excited, allowing for the absorption of light. In contrast, if the d orbitals were higher in energy and far from the ligand orbitals, such transitions would be less favorable, making charge transfer less likely to occur.

Hence, the idea that d orbitals are lower and close to ligand orbitals accurately reflects the interplay necessary for MLCT, highlighting their roles in