Preparation, crystal structures, EPR and reflectance spectra of two new charge-transfer salts, [CpFeCpCH2N(CH3)3]4[XMo12O40] · nCH3CN (n = 0 for X = P or n = 1 for X = Ge)

Two new charge-transfer salts, CpFeCpCH₂N(CH₃)₃]₄PMo₁₂O₄₀] · CH₃CN (1) and CpFeCpCH₂N(CH₃)₃]₄GeMo₁₂O₄₀] (2), were synthesized by the traditional solution synthetic method and their structures were determined by single-crystal X-ray analysis. Salt 1 belongs to the triclinic space group P1, and salt 2 belongs to the triclinic space group . There exist the complex interactions of the cationic ferrocenyl donor and Keggin polyanion in the solid state. The solid state UV-Vis diffuse reflectance spectra indicate the presence of a charge-transfer band climbing from 450 nm to well beyond 900 nm for 1, a charge-transfer band from 460 to 850 nm with λ_max = 630 nm for 2.The EPR spectra of salts 1 and 2 at 77 K show a signal at g = 2.0048 and 1.9501, respectively, ascribed to the delocalization of one electron in reduced Keggin ion in salt 1 and the Mo^VI in GeMo₁₂O₄₀]⁴⁻ is partly reduced to Mo^V owing to the charge-transfer transitions taking place between the ferrocenyl donors and the POM acceptors. The two compounds were also characterized by IR spectroscopy and cyclic voltammetry.