Influence of ancillary ligands on the formation and functionality of oxovanadium(V) metallosupramolecular assemblies:...

A coordination-driven self-assembly approach offers an opportunity for designing metallosupramolecular architectures with tailored properties. Applying this strategy, we present the synthesis and detailed characterization of tetranuclear and polynuclear vanadium(V) compounds with an aroylhydrazone ligand. These assemblies were obtained using the 3-methoxy-2-hydroxybenzaldehyde isonicotinoyl hydrazone ligand (H₂VIH) and NH₄VO₃ in the presence of primary aliphatic alcohols with increasing carbon chain length (from one to five carbon atoms). Reactions of lower alcohols selectively yielded metallocyclic compounds [VO(VIH)(OR)]₄ (1, 2, and 3, where R = CH₃, C₂H₅, and C₃H₇, respectively), while reactions of higher alcohols afforded infinite zig-zag chain polymers [VO(VIH)(OR)] (4 and 5, where R = C₄H₉ and C₅H₁₁, respectively). Their formation was studied experimentally and computationally. Quantum chemical calculations using density functional theory provided valuable insights into the stability of both cyclic and chain assemblies. The solid-state structures of 1-5 and pseudopolymorphs of [VO₂(HVIH)] (6·0.5H2O·0.5CH3OH and 6·2H2O) were confirmed using single-crystal and powder X-ray diffraction methods. The oxovanadium(V) species were tested as catalysts for cyclooctene and benzyl alcohol oxidation, with results correlated with those for analogous molybdenum complexes [MoO₂(VIH)]₄ (7) and [MoO₂(VIH)(C₂H₅OH)] (8). The influence of the metal centre, nuclearity, and ancillary ligand identity on catalytic performance was also investigated, revealing that the vanadium metal center influences the catalytic activity due to its capacity to form robust structures.