Self-assembly of hybrid organic–inorganic polyoxovanadates: functionalised mixed-valent clusters and molecular cages

Abstract

Herein we report the intra- and inter-molecular assembly of a {V₅O₉} subunit. This mixed-valent structural motif can be stabilised as [V₅O₉(L_1–3)₄]^5−/9− (1–3) by a range of organoarsonate ligands (L₁–L₃) whose secondary functionalities influence its packing arrangement within the crystal structures. Variation of the reaction conditions results in the dodecanuclear cage structure [V₁₂O₁₄(OH)₄(L₁)₁₀]⁴⁻ (4) where two modified convex building units are linked via two dimeric {O₄V^IV(OH)₂V^IVO₄} moieties. Bi-functional phosphonate ligands, L₄–L₆ allow the intramolecular connectivity of the {V₅O₉} subunit to give hybrid capsules [V₁₀O₁₈(L_4–6)₄]¹⁰⁻ (5–7). The dimensions of the electrophilic cavities of the capsular entities are determined by the incorporated ligand type. Mass spectrometry experiments confirm the stability of the complexes in solution. We investigate and model the temperature-dependent magnetic properties of representative complexes 1, 4, 6 and 7 and provide preliminary cell-viability studies of three different cancer cell lines with respect to Na₈H₂[6]·36H₂O and Na₈H₂[7]·2DMF·29H₂O.