Synthesis, structure and valence-trapping vs. detrapping for new trinuclear iron pentafluoro benzoate complexes: possible recognition of organic molecules by 57Fe Mössbauer spectroscopy†
Abstract
New mixed-valence trinuclear iron pentafluorobenzoate complexes were synthesized. Their valence-detrapping and/or valence-trapping phenomena were studied by 57Fe Mössbauer spectroscopy and X-ray crystallography. For [Fe3O(C6F5CO2)6(py)3]·CH2Cl2 (1), a valence-trapped state was observed at low temperatures, while the valence-detrapped state was observed at room temperature. Removal of CH2Cl2 from 1 gives the de-solvated [Fe3O(C6F5CO2)6(py)3] (2) where the valence was trapped at room temperature. The CH2Cl2-free 2 can reversibly absorb and desorb CH3CN; the process was followed by 57Fe Mössbauer spectroscopy by monitoring valence-trapping and valence-detrapping phenomena. Organic molecules such as benzene, toluene, ethylbenzene, cumene, and xylene are also trapped by 2 and affect the iron valence states. However, small molecules such as H2O and CO2 do not affect the valence-trapped state of 2. Three xylene isomers trapped within the nano-void of 2 were distinguished by 57Fe Mössbauer spectroscopy at room temperature.