The charge-transfer material TTF-(SVMo11O40)-Mo-IV (TTF = tetrathiafulvalene) was prepared by a spontaneous redox reaction between TTF and the vanadium-substituted polyoxometalate (n-Bu4N)(3)[(SVMo11O40)-Mo-V] in both solution and solid state phases. Single crystal X-ray diffraction gave the stoichiometry TTF4[SVMo11O40]center dot 2H(2)O center dot 2CH(2)Cl(2), with single V atom positionally disordered with eight Mo atoms over the whole alpha-Reggin polyanion [SVMo11O40](4-). Raman spectra support the 1+ charge assigned to the oxidized TTF deduced from bond lengths, and elemental and voltammetric analysis also are consistent with this formulation. Scanning electron microscopy images showed a rod-type morphology for the new charge-transfer material. The conductivity of the solid at room temperature is in the semiconducting range. The TTF and (n-Bu4N)(3)[(SVMo11O40)-Mo-V] solids also undergo a rapid interfacial reaction, as is the case with TTF and TCNQ (TCNQ = tetracyanoquinodimethane) solids. EPR spectra at temperatures down to 2.6 K confirm the presence of two paramagnetic species, V(IV) and the oxidized TTF radical. Spectral evidence shows that the TTF-(SVMo11O40)-Mo-IV materials prepared from either solution or solid state reactions are equivalent. The newly isolated TTF-(SVMo11O40)-Mo-IV material represents a new class of TTF-polyoxometalate compound having dual electrical and magnetic functionality derived from both the cationic and anionic components.