Synthesis, structure and valence-trapping vs. detrapping for new trinuclear iron pentafluoro benzoate complexes: possible recognition of organic molecules by 57 Fe Mössbauer spectroscopy

New mixed-valence trinuclear iron pentafluorobenzoate complexes were synthesized. Their valence-detrapping and/or valence-trapping phenomena were studied by 57 Fe Mössbauer spectroscopy and X-ray crystallography. For [Fe 3 O(C 6 F 5 CO 2 ) 6 (py) 3 ]·CH 2 Cl 2 ( 1 ), a valence-trapped state was observed at low temperatures, while the valence-detrapped state was observed at room temperature. Removal of CH 2 Cl 2 from 1 gives the de-solvated [Fe 3 O(C 6 F 5 CO 2 ) 6 (py) 3 ] ( 2 ) where the valence was trapped at room temperature. The CH 2 Cl 2 -free 2 can reversibly absorb and desorb CH 3 CN; the process was followed by 57 Fe 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 H 2 O and CO 2 do not affect the valence-trapped state of 2 . Three xylene isomers trapped within the nano-void of 2 were distinguished by 57 Fe Mössbauer spectroscopy at room temperature.