Transition metals salts/complexes, high-spin states

Ferromagnetism of the transition and rare-earth metal salts and complexes is due to high-spin states of those atoms. The electronic structure of these metal atoms is open-shell, with d-orbitals and f-orbitals containing several unpaired electrons [1-3]. 

Manganese(II) salts are characteristically very pale pink or colourless. For the Mn + ion in an octahedral high-spin complex, "d-d" transitions are both spin- and Laporte-forbidden (see Section 20.6). Although the electronic spectrum of [Mn(H20)g] + does contain several absorptions, they are all weaker by a factor of sslO than those arising from spin-allowed transitions of other first row metal ions. The weak absorptions observed for Mn + arise from promotion of an electron to give various excited states containing only three unpaired electrons. 

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