Architectural control of urea in supramolecular 1D strontium vanadium oxide chains

Abstract

A facile bottom-up approach for the controlled self-assembly of infinite strontium vanadium oxide chains is presented. Two novel one-dimensional strontium-linked polyoxovanadate chains have been isolated by linkage of decavanadate clusters with strontium(ii) ions. To control the architecture dimensions, urea was used as a critical control parameter which allowed tuning of the intra- and intermolecular spacings within the crystal lattice. Using N,N-dimethyl formamide (DMF) and urea as stabilizing ligands, a supramolecular structure, {[Sr(dmf)3(CON2H4)2][Sr(dmf)2(CON2H4)2][H2V10O28]} (1) was obtained where cluster linkage is achieved through urea-bridged strontium dimers. In the absence of urea, a purely strontium-linked supramolecular architecture, {[Sr(dmf)4]2[H2V10O28]} (2), is formed. The chain architectures were characterized by single crystal X-ray diffraction, elemental analysis, UV-Vis and FT-IR spectroscopy. In order to learn about the assembly and dis-assembly of 1D architectures ESI-mass-spectrometry was performed. The results show how simple organic ligands may be used to engineer the crystal lattice and illustrate that further work is needed to understand the exact mode of action of the urea ligands.

Solvent-Controlled Polymerization of Molecular Strontium Vanadate Monomers into 1D Strontium Vanadium Oxide Chains

“…Here, we explore the possibility of linking individual {V 12 } units into supramolecular chains, similar to a classical organic polymerization. To avoid additional complexities arising from the use of redox-active linkage metal ions, we opted to use strontium-functionalized dodecavanadates, as in previous studies we had successfully linked decavanadate clusters using Sr 2+ cations …”

“…Pioneering work highlighted the assembly of multidimensional framework materials formed by linking mixed-valent polyoxovanadates with 3d transition metals or alkaline earth metals . Furthermore, POMs were linked via Ag I -based bridging units which has led to several 1D chains and 2D grids. − Later studies were focused on the linkage of POMs through transition metals or lanthanides, leading to a multitude of supramolecular aggregates. − Based on these guiding design principles, we have recently started to explore the linkage of vanadium oxide clusters with large alkali or alkaline earth metals as potential models for industrial catalysts, e.g., those used in the oxidative dehydrogenation of alkanes. − By the use of Sr II or Ba II cations, we gained access to a series of large supramolecular clusters and 1D strontium or barium vanadium oxide chains . In these studies, we noted that the bulkiness of the solvent ligands employed significantly affects the resulting supramolecular architectures. − Further architectural control was achieved by using additional organic linkers such as urea …”

The use of mixed-metal single source precursors for the synthesis of complex metal oxides

“…26,27 In recent years, many M-POV structures have been reported, many of these are yet untested as SSPs. For example, could [Sr(DMF)2.5(CON2H4)2]2[H2V10O28] (DMF=dimethylformamide) and (n-Bu4N)4[Cu6V30O82(NO3)2(CH3CN)6], 124,125 access MV2O6 (M = Sr, Cu) materials useful as sensors, photocatalysts and photoanodes? 126,127…”

pH-induced phase transition and crystallization of soft-oxometalates (SOMs) into polyoxometalates (POMs): a study on crystallization from colloids

“…Several studies have been reported on the formation of 1D POM chains, comprised of barium vanadates (Kastner & Streb, 2013), tetrarubidium decavanadates (Yakubovich et al, 2015), strontium vanadium oxides (Schwarz & Streb, 2015) and octamolybdates (Rosnes et al, 2012), but the phenomenon behind their formation was not discussed. In this work, we demonstrate a simple one-pot synthetic method for growing 1D inorganic chains of K(C 6 H 16 N) 3 Mo 8 O 26 ÁH 2 O from its colloidal phase through the variation of pH.…”