Synthesis, isolation, spectroscopic and structural characterization of a new pH complex structural variant from the aqueous vanadium(V)-peroxo-citrate ternary system |
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Authors: | M. Kaliva C. Gabriel C.P. Raptopoulou J.-P. Tuchagues |
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Affiliation: | a Laboratory of Inorganic Chemistry, Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece b Chemical Process Engineering Research Institute, Thermi, Thessaloniki 57001, Greece c Department of Chemistry, University of Crete, Heraklion 71409, Greece d Institute of Materials Science, NCSR “Demokritos”, Aghia Paraskevi 15310, Attiki, Greece e Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, 31077 Toulouse Cedex, France |
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Abstract: | In a pH-specific fashion, V2O5, citric acid and H2O2 reacted at pH 5.5-6.0 and afforded a red crystalline product at 4 °C. Elemental analysis pointed to the molecular formulation . Complex 1 was further characterized by UV/Vis, FT-IR, NMR, cyclic voltammetry, and X-ray crystallography. The X-ray structure of 1 reveals two dinuclear vanadium-peroxo-citrate subunits, A and B, linked through a hydrogen bond. In both A and B, the citrate ligands have different protonation states, ultimately affording a pentagonal bipyramidal geometry around each V(V) ion. The peroxide ligands bind V(V) in a side-on fashion. pH-Dependent, non-thermal and thermal transformations of 1 unravel its connection with key participants in the vanadium-peroxo-citrate ternary system and project its association with other non-peroxo binary complexes of variable vanadium oxidation state, geometry, citrate binding mode and state of protonation. Overall, the surprising twist in the aqueous synthetic chemistry of the investigated ternary system: (a) projects a new pH structural variant (species A) as a component of the speciation; (b) provides an in-depth look at that speciation under specific pH conditions; and (c) offers significant insight into the aqueous structural speciation of vanadium with peroxide and citrate, and its potential relevance to biological processes. |
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Keywords: | Vanadium-citrate-peroxo compounds X-ray structure Insulin mimetic vanadium Structural speciation Chemical reactivity |
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