UV-visible, XANES and EXAFS investigations of a cobalt complex grafted in micelle templated silica

The coordination of the trans-[Co(en)(2)Cl-2](+) ion exchanged on as-synthe sized micelle-templated silica (MTS) is investigated using X-ray absorption near edge structure (XANES), Extended X-ray absorption fine structure (EXA FS) and diffuse reflectance UV-visible spectroscopies. XANES and UV-visible data show that most of the adsorbed complexes adopt the cis configuration and that both chloride ligands are likely substituted during the displaceme nt of the templating surfactants. This is confirmed by EXAFS the multiple s cattering analysis of which reveals the formation of a single Co-O-Si bridg e; the Co-O and Co-Si bond lengths are 1.91 +/- 0.03 and 3.22 +/- 0.03 Angs trom, respectively. According to pH considerations, the second substitution position is occupied by a hydroxy group which leads to a grafted complex f ormula of cis-[Co(en)(2)(OH)(drop SiO)]Cl. A direct synthesis of Go-MTS usi ng the same cobalt complex does not lead to mononuclear grafted species.