Molecular Precursors of Mixed Oxide Materials for Sensor Applications and Molecular Imaging

Abstract

Cation-doped perovskite materials based on barium titanate, such as (Ba,Sr)(Ti,Nb)O₃, are of interest as transparent ceramic semiconductors with conductivity strongly dependent both on the cation and the oxygen stoichiometry. Development of precursor systems offering proper control over the cation stoichiometry and permitting to efficiently avoid residual carbon impurities is therefore an important problem. In the present communication we report the synthesis and structural characterization of a series of hetero-metallic precursors of these materials with the general formulae M₂ ^IITi₂(L)₄(OR)₈(ROH)₂ and M₂ ^IIM₂ ^V(L)₂(OR)₁₂(ROH)₂, where R = Et, ⁿPr; M^II = Ba, Sr; M^V = Nb, Ta; L = thd or R’OAcAc (R’ = ^tBu, ⁱPr). The compounds have been characterized by single crystal and power X-ray and by ¹H and ¹³C NMR, vibration spectroscopy and mass-spectrometry. These species are very stable in solution and display even considerable gas phase stability. Solution microhydrolysis of the molecules in these series leads most often to oxo-aggregates with the cation stoichiometry rather close to 1:1, which additionally simplifies handling of solutions based on these precursors. The obtained precursors have been used for preparation of powders and films (on Si substrates), which were characterized by SEM-EDS and X-ray powder techniques.