Metal complexes in inorganic matrixes .15. Coordination of metal ions by lysinate-modified titanium and zirconium alkoxides and the preparation of metal/titania and metal/zirconia nanocomposites

The substituted metal alkoxides (EtO)(3)Ti(lysinate) or (BuO)(3)Ti(lysinate) are obtained when 1 equiv of lysine is added to Ti(OEt)(4) or Zr(OBu)(4). While the alpha-amino carboxylate moiety chelates the titanium or zirconium atom, the terminal amino group is capable of coordinating a metal ion. According to spectroscopic data, the complexes (AcO)(2){M[NH2(CH2)(4)CH(NH2)COO]E(OR)(3)](4)} (M=Co, Ni, Cu; E=Ti,Zr) are formed upon addition of M(OAc)(2) to ethanolic solutions of(RO)(3)E(lysinate). The coordination of lysine and of the late transition metal ions is retained during sol-gel processing. There is no leaching of Co, Ni, or Cu ions from the metal complex-containing gels (AcO)(2){M[NH2(CH2)(4)CH(NH2)COO]EO(3/2)](4)}. Upon oxidation of the gels in air at 500 degrees C, nanosized CoTiO3 and NiTiO3 particles in TiO2, CuO particles in TiO2, or MO particles in ZrO2 were obtained. Subsequent reduction with hydrogen at 500 degrees C resulted in metallic nanoparticles dispersed in titania or zirconia. Composites of the same composition were prepared from unmodified E(OR)(4) and M(OAc)(2) for comparison. There is no systematic influence of the lysinate coordination on the metal particle size and size distribution of the final composites.