For tetrahedral complexes, what is the approximate Emax value?

In the context of tetrahedral complexes, the Emax value, which refers to the maximum molar absorptivity or extinction coefficient in a spectroscopic measurement, is closely related to the electronic transitions occurring within the complex. Tetrahedral complexes generally exhibit a smaller ligand field splitting compared to their octahedral counterparts due to the geometry and arrangement of ligands around the central metal ion.

The ligand field splitting in tetrahedral coordination leads to electronic transitions that typically result in absorbance maxima around 250 nm. This specific range corresponds to the energy difference between the d-orbitals influenced by the tetrahedral coordination environment. As sigma donor ligands and field strength can also affect spectral properties, tetrahedral complexes with certain ligands may exhibit slight variations in their Emax values.

However, for many common tetrahedral complexes involving transition metals, the absorbance peaks commonly lie in the vicinity of 250 nm. Therefore, selecting the value of 250 aligns with the observed behavior of these complexes within the expected range.