Synthesis, Mossbauer, Cyclic Voltammetry, Magnetic Properties And Molecular Structures Of The Low-Spin Iron(Iii) Bis(Pyrazine) Complexes With The &Itpara&It-Fluoro And &Itpara&It-Chloro Substituted &Itmeso&It-Tetraphenylporphyrin

Two new bis(pyrazine) iron(III) meso-porphyrin complexes are reported here: the bis(pyrazine) [5,10,15,20-tetra(para-fluoro-phenyl)porphyrinato]iron(III) triflate; [Fe(TFPP)(pyz )(2)]SO3CF3 (1) and the bis(pyrazine)[5,10,15,20-tetra(para-chlorophenyl)porphyrinato]iron(III) triflate; [Fe(TCI PP)(Pyz )(2)]SO3CF3 (2). The X-ray molecular structures of 1-2 show that the planes of the two pyrazine axial ligands are perpendicular and that the porphyrin macrocycles of these derivatives are very distorted, leading to a short average equatorial iron-pyrrole N atoms distance appropriate for low-spin ferric porphyrinates. The Mossbauer data of 1-2 feature relatively low values of the quadrupole splitting (Delta E-Q similar to 1.20 mm.s(-1)) appropriate for low-spin Fe(III) metalloporphyrin with perpendicular orientation of N-donor planar ligands. The temperature dependence of the magnetic susceptibility and the magnetization curves have shown that the results for complexes 1-2 confirm the low-spin state of our two-ferric species, while the cyclic voltammetry data show that the half potential [Fe(III)/Fe(II)] values are shifted anodically compared to the beta-pyrrole substituted porphyrin octaethylporphyrin with parallel bis(N-donor) planar axial ligands. (C) 2018 Elsevier B.V. All rights reserved.