Structure and bonding of [VIVO(acac)2] on the surface of AlF3 as studied by pulsed electron nuclear double resonance and hyperfine sublevel correlation spectroscopy

Abstract

Well defined isolated [V^IVO(acac)₂] surface complexes have been prepared on aluminium trifluoride, α-AlF₃, as solid support by equilibrium adsorption from liquid solution. The paramagnetic vanadium(IV) surface complexes were studied by pulsed electron spin resonance spectroscopy in combination with quantum chemical calculations using density functional theory. ¹⁹F and ²⁷Al ligand hyperfine interactions with the nuclei of the AlF₃ support observed by pulsed electron nuclear double resonance and hyperfine sublevel correlation spectroscopy experiments verify the direct chemical bonding between the vanadium and a surface fluorine atom. Detailed analysis of the ligand hyperfine couplings supported by quantum chemical calculations indicates that the axial position of [V^IVO(acac)₂]trans to the oxo ligand is bound directly to a terminal fluorine atom of the support. Analysis of the ¹H ligand hyperfine interaction revealed that an acidic H⁺ of the AlF₃ surface protonated a donor oxygen of the acetylacetone ligand in the surface complex.