Supramolecular structures in oxovanadium(IV) compounds with pyrid-2-one and pyrid-4-one ligands

Abstract

The aim of this study is to perform an analysis of the spectroscopic and electronic properties of three vanadium(IV) complexes formed from bis(acetylacetonato)oxovanadium(IV) [VO(acac)2] and pyrid-2-one (2pyon) or pyrid-4-one (4pyon) ligands: [VO(acac)2(2pyon)] (1), [VO(acac)2(4pyon)] (2) and [VO(acac)2(H2O)]·4pyon (3). In 1 and 2, the pyridone ligand coordinates neutral and monodentate to the vanadium center, with the oxygen atom placed in the axial trans position to the oxo ligand. In 3, the 4pyon ligand remains outside the metal first coordination sphere but bound to the aqua ligand through hydrogen bonds that led to the formation of a supramolecular structure. Moreover, the Density Functional Theory (DFT) were applied to answer two overarching aspects. First, in complexes 1 and 2, the DFT analysis was used to establish the most stable configuration among the vanadium pyridone complex isomers, comparing the ligand via O-bound pyridone and N-bound hydroxypyridine chelating modes. Second, DFT was also performed to enable understanding of the intermolecular interactions between the 4pyon and the [VO(acac)2(H2O)] moiety to elucidate the intermolecular interactions in 3. Further insights were also obtained by applying the Natural Bond Orbital analysis (NBO) along with a topological perspective via the use of the Quantum Theory of Atoms in Molecules (QTAIM).