RESUMO
We report here a facile synthetic and analytical approach that allows us to identify and characterize functionalized polyoxomolybdate clusters that form upon the partial reduction of Mo(VI) salts in the presence of organoarsonate ligands. We demonstrated that electrospray ionization mass spectrometry, in combination with X-ray crystallography, provides an extremely powerful tool, allowing us to exploit slight perturbations of the ligand structures for the preparation of a series of unprecedented cluster compounds. Redox-active transition metals that adopt cubane or related structures are of particular interest because of their resemblance to active sites of enzymes. Our investigations underline the stability of the hybrid compounds in solution, an essential requirement for potential applications as catalysts. Supplemental analyses include measurements of the magnetic properties, NMR, IR, UV/vis, and bond-valence-sum analyses. Our results highlight the possibility of exploring real-time growth reactions of polyoxometales that emerge in solution and transform to produce hybrid organic-inorganic polyoxometalate clusters.
RESUMO
Resveratrol, trans-epsilon-viniferin and trans-delta-viniferin are the major stilbenes induced in downy mildew infected grapevine leaves. In addition, nine minor polyphenolic compounds, described as stilbenes derivatives, have been separated and detected among known stilbenes after a methanolic microextraction of small pieces (1-2 mg) from infected grapevine leaves with a rapid, qualitative and optimized HPLC method coupled to mass spectrometry using atmospheric pressure photoionisation (APPI-MS(n)). The characterization of unknown stilbenic derivatives as six resveratrol dimers, two dimethylated resveratrol dimers and a resveratrol trimer are reported. Therefore, structures have been proposed for the dimethylated resveratrol dimers. Use of an easy sample treatment and the LC-APPI-MS(n) method results in spectral data of these minor naturally occurring viniferin analogues.
