A theoretical study of the energy-transfer process in [Eu⊂bpy.bpy.bpy]3+ cryptates: a ligand-to-metal charge-transfer state?

A complete theoretical model to calculate the luminescent properties of lanthanide coordination compounds is used to analyze the emission quantum yield of the [Eu⊂bpy.bpy.bpy]3+ and [Eu⊂bpy.bpy.bpy]3+·2H2O compounds. This theoretical model includes the calculation of the molecular structure, of the ligand electronic structure, of the ligand–lanthanide energy-transfer, of the temporal dependence of the ligand and lanthanide populations, which lead to the emission quantum yield, relative emission intensity and lifetime of the emitting state. In the present case, this theoretical approach was used to ascertain the presence of a ligand-to-metal charge-transfer (LMCT) state in these compounds. In addition, this approach has provided indications of the location of the LMCT state as well as of the magnitudes of the energy-transfer rates involving this state.