Engineering two cooperative sites into a catalyst implies
the onset
of synergistic effects related to the existence of short-range electronic
interactions between two metal components. However, these interactions
and the relative structure–property correlations are often
difficult to obtain. Here we show that hyperfine spectroscopy has
the potential to reveal the presence of V4+–O–Mo6+linkages assessing the degree of spin density transfer from
paramagnetic V4+species to proximal oxo-bridged Mo6+metal ions. The dimer species were prepared by adsorption
of Mo(CO)6in the pores of SAPO-5, followed by thermal
decomposition and oxidation and subsequent grafting of anhydrous VCl4(g) followed by hydrolysis and dehydration. The metal species
react with SAPO protons during the exchange process and generate new
Lewis acid sites, which act as redox centers. X- and Q-band EPR and
HYSCORE experiments have been employed to monitor the local environment
of V4+species obtaining direct evidence for spin delocalization
over27Al,31P,95Mo, and97Mo nuclei, demonstrating the presence of bimetallic V–O–Mo
well-defined structures.