A one-dimensional supramolecular chain based on [H2V10O28]4− units decorated with 4-dimethylaminopyridinium ions: an experimental and theoretical characterization†
The compound [DMAPH]4[H2V10O28]·5H2O (1), where DMAPH is a 4-dimethylaminopyridinium ion [C7H11N2]+, crystallized in a monoclinic cell (space group P21/n). The X-ray analysis revealed that the protic units [H2V10O28]4− are linked via cyclic double hydrogen bonds forming a 1D supramolecular structure along the  direction, which is decorated by DMAPH cations via close N–H⋯O contacts (dH⋯O = 1.88 Å). The experimental IR and Raman spectra of this compound are characterized by strong and medium bands in the 1000–400 cm−1 region, attributed to stretching and bending modes of the V–O bonds. DFT-D3/CPCM methods were used to further study the vibrational modes of both [V10O28]6− and [H2V10O28]4− anions and also of compound 1. For all compounds, the region of 990–860 cm−1 showed the modes corresponding to the symmetric V–O–H bending coupled with the VO stretching of the decavanadate moiety. Aqueous 51V NMR spectroscopy showed the classical resonances for the V5+ octahedral centers found in the decavanadate ion. Non-covalent interactions in the supramolecular structure were studied by analysis of topological parameters by QTAIM. The nature of the [H2V10O28]4− unit as a donor/acceptor group was explored using 2D-fingerprint plots obtained from the molecular Hirshfeld surface. Given the structural characteristics of [DMAPH]4[H2V10O28]·5H2O, it could be suggested that this compound could act as a slow releasing prodrug of the decavanadate ion, species that have been useful as an antidiabetic agent in type 1 and type 2 rat models of diabetes mellitus.