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Spin-Crossover in a Pseudo-tetrahedral Bis(formazanate) Iron Complex

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posted on 14.04.2016, 00:00 authored by Raquel Travieso-Puente, J. O. P. Broekman, Mu-Chieh Chang, Serhiy Demeshko, Franc Meyer, Edwin Otten
Spin-crossover in a pseudo-tetrahedral bis­(formazanate) iron­(II) complex (1) is described. Structural, magnetic, and spectroscopic analyses indicate that this compound undergoes thermal switching between an S=0 and an S=2 state, which is very rare in four-coordinate complexes. The transition to the high-spin state is accompanied by an increase in Fe–N bond lengths and a concomitant contraction of intraligand N–N bonds. The latter suggests that stabilization of the low-spin state is due to the π-acceptor properties of the ligand. One-electron reduction of 1 leads to the formation of the corresponding anion, which contains a low-spin (S=1/2) Fe­(I) center. The findings are rationalized by electronic structure calculations using density functional theory.