Nano-architecture of silica nanoparticles as a tool to tune both electrochemical and catalytic behavior of Ni II @SiO 2 .

The present work introduces a facile synthetic route for efficient doping of [Ni II (bpy) x ] into silica nanoparticles with various sizes and architectures. Variation of the latter results in different concentrations of the Ni II complexes at the interface of the composite nanoparticles. The UV-Vis analysis of the nanoparticles reveals changes in the inner-sphere environment of the Ni II complexes when embedded into the nanoparticles, while the inner-sphere of Ni II is invariant for the nanoparticles with different architecture. Comparative analysis of the electrochemically generated redox transformations of the Ni II complexes embedded in the nanoparticles of various architectures reveals the latter as the main factor controlling the accessibility of Ni II complexes to the redox transitions which, in turn, controls the electrochemical behavior of the nanoparticles. The work also highlights an impact of the nanoparticulate architecture in catalytic activity of the Ni II complexes within the different nanoparticles in oxidative C-H fluoroalkylation of caffeine. Both low leakage and high concentration of the Ni II complexes at the interface of the composite nanoparticles enables fluoroalkylated caffeine to be obtained in high yields under recycling of the nanocatalyst five times at least.