UV-Vis spectrum in high spin and low spin conditions in octahedral Fe+2 complexes: The role of symmetry

Spin-crossover phenomenon, especially in the first transition elements d4-d7 electron configuration is observed in octahedral complexes. This feature is used in some technological applications. In these complexes, electron configurations differ in low spin and high spin states. In these complexes, especially Fe+2 can easily switch from high spin state to low spin state or from low spin state to high spin state under temperature, pressure and electromagnetic radiation. In the low spin state, the ground-term symbol of the metal will be A2g, while the symbol in the high spin state will be T. Therefore, the UV transition in the low spin state will differ compared to the high spin state. In this study, we examined the UV-Vis transition in certain produced complexes for both cases. At the end of the examination, we saw that symmetry is very important in these transitions. We found that while the UV-absorption coefficient was low for the fully symmetrical A term, it was partially high for T.