Mechanistic insights into template-driven polyoxovanadate self-assembly: the role of internal and external templates

Abstract

The self-assembly of molecular metal oxides, polyoxometalates (POMs), can be controlled using internal or, more rarely, external templates. Here, we explore how the interplay between internal templates (halides, oxoanions) and organic external templates (protonated cyclene species) affect the self-assembly of a model polyoxovanadate cluster, [V₁₂O₃₂X]ⁿ⁻ (X = Cl⁻, Br⁻, NO₃⁻). A combination of crystallographic analyses, spectroscopic studies and in situ as well as solid-state ⁵¹V NMR spectroscopy provide critical insights into the initial formation of an intermediate vanadate species formed during the process. Structural and spectroscopic studies suggest that a direct interaction between internal and external templates allows tuning of the internal template position within the cluster cavity. These insights form the basis for further developing the template-driven synthetic chemistry of polyoxovanadates.