Continuous Wave and Pulse EPR Characterization of Open-Shell Ti3+ Ions Generated in Hybrid SiO2–TiO2 Monoliths

Open-shell Ti3+ ions are generated within hybrid SiO2– TiO2 mesoporous monoliths by reaction with triethylaluminium vapors. Continuous wave and 2D pulse electron paramagnetic resonance techniques are used to investigate the local coordination environment of the Ti3+ species through detection of hyperfine interactions of the unpaired electron with magnetically active nuclei of the matrix, including natural abundant framework 29Si. The results provide evidence for the reducing power of triethylaluminium towards isolated Ti4+ ions through the formation of open-shell Ti3+ ions atomically dispersed and fully incorporated in the SiO2 framework with a local structure similar to that of titanium silicalite and no segregation of TiO2 phases at this level of Ti doping.