Spontaneous Redox Synthesis of the Charge Transfer Material TTF4[SVMo11O40]

The charge-transfer material TTF-SVIVMo11O40 (TTF = tetrathiafulvalene) was prepared by a spontaneous redox reaction between TTF and the vanadium-substituted polyoxometalate (n-Bu4N)3[SVVMo11O40] in both solution and solid state phases. Single crystal X-ray diffraction gave the stoichiometry TTF4[SVMo11O40]·2H2O·2CH2Cl2, with the single V atom positionally disordered with eight Mo atoms over the whole α-Keggin 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[SVVMo11O40] 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-SVIVMo11O40 materials prepared from either solution or solid state reactions are equivalent. The newly isolated TTF-SVIVMo11O40 material represents a new class of TTF-polyoxometalate compound having dual electrical and magnetic functionality derived from both the cationic and anionic components.