Synthesis of 1-(1-ferrocenylethyl)-pyridinium chloride and its hybrid materials with lindquist-type polyoxometalates

Abstract A new ferrocene derivative, 1-(1-ferrocenylethyl)-pyridinium (fep = CpFeCp–CH(CH 3 )–Py + ) chloride, and two charge-transfer salts (CTSs) based on the cationic fep donor and Lindqvist-type polyoxometalate acceptors, [fep] 2 [Mo 6 O 19 ] ( 1 ) and [fep] 2 [W 6 O 19 ] ( 2 ), were synthesized. fepCl was characterized by elemental analysis, IR spectroscopy and 1 H NMR and the two CTSs were characterized by elemental analysis, IR spectroscopy, UV–vis diffuse reflectance spectrum, cyclic voltammetry, fluorescence spectrum and single crystal X-ray diffraction. X-ray crystallographic studies of the brownish red CTSs 1 and 2 reveal that they are isostructural and crystallize in the monoclinic space group P 2 1 / n . In salts 1 – 2 , fep and polyoxoanions are cocrystallized by Coulombic forces, and there also exist the complex C–H⋯π and π⋯π stacking interactions between the adjacent fep cations and C–H⋯O hydrogen bonds between the adjacent fep cations and polyanions. The UV–vis diffuse reflectance spectra indicate the presence of a broad charge-transfer band between 500 and 850 nm for 1 – 2 , and CT character of 1 and 2 is also confirmed by the Mulliken correlation between the CT transition energies and the reduction potentials of the polyoxometalate acceptors.