Electrochemical and Structural Characterization of Soft Landed Tungsten-Substituted Lindqvist Polyoxovanadate-Alkoxides

Abstract

Lindqvist polyoxovanadate-alkoxide (POV-alkoxide) clusters are excellent candidates for applications in energy storage and conversion due to their rich electrochemical profiles. One approach to tune the redox properties of these cluster complexes is through substitutional cationic doping within the hexavanadate core. Here, we report the synthesis of a series of tungsten-substituted POV-alkoxide clusters with one and two tungsten atoms. Soft landing of mass-selected ions was used to purify heterometal POV-alkoxides that cannot be readily separated using conventional approaches. The soft landed POV-alkoxides are characterized using infrared reflection-absorption spectroscopy and electrospray ionization mass spectrometry. The redox properties of the isolated ions are examined using an in situ electrochemical cell which enables traditional in vacuo electrochemical measurements inside of an ion soft landing instrument. Although the overall cluster core retains redox activity after tungsten doping, vanadium-based redox couples (V^V /V^IV ) are shifted substantially, indicating a pronounced effect of a heteroatom on the electronic structure of the core.

Keywords: heterometallic complexes; ion soft landing; mass spectrometry; tungstates; vanadates; voltammetry.