The development of single-site transition metal centers in metal-organic complexes at surfaces is of interest to advance selectivity of heterogeneous catalysts. In this study, we have examined the chemical reactivity of O2 with one-dimensional metal-organic chains consisting of 3,6-di(2-pyridyl)-1,2,4,5-tetrazine (DPTZ) and vanadium cations. The chains self-assemble through an on-surface redox process on the Au(100) surface. The surface was characterized using X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). Exposing the V-DPTZ chains to oxygen results in the oxidation of vanadium from VII to VIV with a saturation of one O atom per V atom. STM shows that the long-range ordering of the chains is disrupted initially, but can be recovered by annealing. By contrast, metallic V nanoparticles on the same surface oxidize only to VIII under the same conditions. Those particles have kinetic limitations that restrict the oxidation to the particle edges, but the oxidation becomes more uniform after annealing. This oxidation behavior of metallic V nanoparticles is quite different from the growth of V2O3 nanoparticles by vapor deposition of V in O2, which particles are uniformly oxidized to VIII and are stable under annealing.

Reactivity of O2 with single-site, low-valent vanadium in metal-organic chains at surfaces

254th National Meeting (2017)

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