Homogeneous and Heterogeneous Anion Sensing by a Molecular Cobalt-Vanadium Oxide.

Spectroscopic anion sensing is a vital non-invasive tool in chemistry and biology. Here, a molecular cobalt-vanadium-oxide cluster was shown to be capable of selectively binding and detecting various mono-anions in solution and immobilized on a solid support. The cluster anion [Co(X)V O ] (X=mono-anion, for example, halide, pseudohalide, carboxylate, etc.) was formed spontaneously upon anion addition by self-assembly in solution. The cluster showed distinct spectral changes upon anion binding that could be followed spectroscopically and visually owing to a significant change of the solution color. DFT computations showed that the anion binding observed experimentally was correlated to the relative cluster stabilities. Competitive-binding studies showed that selective anion binding was possible from a mixture of anions. Immobilization of the anion sensor on silica strips provided access to single-use dip-stick sensors for the facile detection of anions in solution. The system presented enables the development of homogeneous or heterogeneous molecular anion sensors with possible applications in chemistry, bio-medical scenarios, and under harsh environmental conditions.