Zr4+^{4+} solution structures from pair distribution function analysis

The structures of metal ions in solution constitute essential information for obtaining chemical insight spanning from catalytic reaction mechanisms to formation of functional nanomaterials. Here, we explore Zr$^{4+}$ solution structures using X-ray pair distribution function (PDF) analysis across pH (0–14), concentrations (0.1–1.5 M), solvents (water, methanol, ethanol, acetonitrile) and metal sources (ZrCl$_4$, ZrOCl$_2$·8H$_2$O, ZrO(NO$_3$)$_2$·xH$_2$O). In water, [Zr$_4$(OH)$_8$(OH$_2$)$_{16}$]$^{8+}$-tetramers are predominant, while non-aqueous solvents contain monomeric complexes. The PDF analysis also reveals second sphere coordination of chloride counter ions to the aqueous tetramers. The results are reproducible across data measured at three different beamlines at the PETRA-III and MAX IV synchrotron light sources