A Density Functional Study of the Spin State Energetics of Polypyrazolylborato Complexes of First-row Transition Metals

Density Functional Theory (DFT) was used to analyse and explain spin state energetics of first-row transition metals (Mn(II), Fe(II), Co(II); Cr(III), Mn(III), Fe(III), Co(III); Mn(IV)) in polypyrazolylborato complexes. We explored the effects of substitutions at the 3 and 5 positions of the pyrazolyl rings, as well as the influence of Jahn-Teller (JT) distortions on spin-state switching. Although the stabilizations due to JT distortion are sometimes substantial, this does not lead to switching of the spin ground-state. On the other hand, electron withdrawing or donating substituents do lead to significant changes in the spin-crossover (SCO) properties of the investigated complexes.