Charge Transfer Spectrum
An intense absorption produced when an electron moves between metal and ligand orbitals.
Unit
nm
In depth
Charge transfer transitions are fully allowed, so they are one to two orders of magnitude more intense than d–d transitions. They may be ligand-to-metal or metal-to-ligand, and they account for the vivid colours of compounds that contain no d electrons at all.
Examples in the real world
The deep purple of MnO₄⁻ and the orange of Cr₂O₇²⁻, both d⁰ ions with no possible d–d transition.