Structural, Spectroscopic, and Chemical Properties of the First Low-Spin Iron(III) Semiquinonate Complexes in the Solid State and in Solution

Abstract

oxygen molecule on the iron(iii) catecholate moiety.

Iron(III) Spin Crossover Compounds

“…A low spin$intermediate spin transition has also been found for a unique Fe(III) compound having an octahedral FeN 4 S 2 environment [126]. In this compound the Fe(III) ion is surrounded by the tetradentate N-donating macrocycle N,N 0 -dimethyl-2,11-diaza [3.3](2,6)pyridinophane together with the bidentate S-donating 1,2-benzenedithiolate, which occupies the cis positions in the equatorial plane.…”

“…For sixcoordinate systems the spin crossover generally involves an S=1/2$S=5/2 change, whereas for five-coordinate materials an intermediate (quartet) spin state is involved in S=1/2$S=3/2 transitions. There is just one report of such a transition in a six-coordinate system and that is considerably distorted [126].…”

DFT studies of cobalt hydride intermediate on cobaloxime‐catalyzed H2 evolution pathways

“…Even though the triplet states were predicted to be the lowest lying ground state, the energy separation computed for the singlet and triplet states was only 2.7 Kcal/Mol for 10 and 6.7 Kcal/Mol for 11 . The small energetic separation indicated the spin crossover behavior between singlet and triplet states 38–40 . 10 could only be obtained at the singlet state because both the triplet and quintet states were quite unstable with the result that HH was separated far from cobaloxime plane (over 3.5 Å) (Fig.…”

Tuning the Electronic Structure of Halidobis(o-imino-benzosemiquinonato)iron(III) Complexes

“…The binding of a Fe III ion to open‐shell (“noninnocent”), π‐radical ligands such as phenoxyls2a or o ‐benzosemiquinonates2b inevitably induces a strong intramolecular, antiferromagnetic spin coupling between the magnetic orbitals of the π radicals and the available metal‐centered, half‐filled t 2g orbitals of the Fe III ion. This gives rise to electronic ground states ranging from S t =22a,2b to S t =02c depending on the number of coordinated radicals and the actual local spin state at the Fe III ion in a given compound. O , N ‐coordinated o ‐aminophenolates have been shown to be readily oxidized by air to yield the corresponding o ‐iminobenzosemiquinonates, (L ISQ ) − 3, 4.…”