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Iron 10‐Thiacorroles: Bioinspired Iron(III) Complexes with an Intermediate Spin ( S =3/2) Ground State
Author(s) -
Sakow Dimitri,
Baabe Dirk,
Böker Birte,
Burghaus Olaf,
Funk Markus,
Kleeberg Christian,
Menzel Dirk,
Pietzonka Clemens,
Bröring Martin
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201303786
Subject(s) - chemistry , spin crossover , crystallography , ligand (biochemistry) , pyridine , spin states , ground state , electron paramagnetic resonance , cationic polymerization , mössbauer spectroscopy , inorganic chemistry , nuclear magnetic resonance , polymer chemistry , medicinal chemistry , atomic physics , biochemistry , physics , receptor
A first systematic study upon the preparation and exploration of a series of iron 10‐thiacorroles with simple halogenido (F, Cl, Br, I), pseudo‐halogenido (N 3 , I 3 ) and solvent‐derived axial ligands (DMSO, pyridine) is reported. The compounds were prepared from the free‐base octaethyl‐10‐thiacorrole by iron insertion and subsequent ligand‐exchange reactions. The small N 4 cavity of the ring‐contracted porphyrinoid results in an intermediate spin (i.s., S =3/2) state as the ground state for the iron(III) ion. In most of the investigated cases, the i.s. state is found unperturbed and independent of temperature, as determined by a combination of X‐ray crystallography and magnetometry with 1 H NMR‐, EPR‐, and Mössbauer spectroscopy. Two exceptions were found. The fluorido iron(III) complex is inhomogenous in the solid and contains a thermal i.s. ( S =3/2)→high spin (h.s., S =5/2) crossover fraction. On the other side, the cationic bis(pyridine) complex resides in the expected low spin (l.s., S =1/2) state. Chemically, the iron 10‐thiacorroles differ from the iron porphyrins mainly by weaker axial ligand binding and by a cathodic shift of the redox potentials. These features make the 10‐thiacorroles interesting ligands for future research on biomimetic catalysts and model systems for unusual heme protein active sites.