Synthesis And Post-functionalization Of Organic Derivatives Of Mix-valence Hexavanadates

Polyoxometalates?POMs?are polyoxometallic anions formed by polycondensation of the early transition metal ions and oxygen anions,which have unique structures and various properties.Organic modification has significant means to the materialization and practical application of the POMs as it can adjust and improve the properties of POM clusters.Polyoxovanadates?POVs?is an important kind of POMs,which have potential applications in the fields such as catalysis,pharmaceutical and magnetic materials.However,the organic modification of POVs is still less developed and the reported organic derivatives of POVs have a few drawbacks such as structural similarity and single valence,which have hindered the property studies and practical applications of the POVs.Especially,the organic derivatives of the mixed-valence POV are rarely reported.In this paper,a new protocol for the preparation of mixed-valence POVs by hydrothermal synthesis was developed which uses metavanadate salts as reactant and hydrazine as reducing agent.This method is suitable for batch synthesis as it has the advantages of high yield,easy separation and purification,cheap and low-toxic raw materials,which laid an important foundation for in-depth study of the mixed-valence POVs.Four mixed-valence or fully reduced trimethylol trisubstituted hexavanadates H₂[VIV₃VV₃O₁₀{NH₂C?CH₂O?₃}₃] ? 10H₂ O,Na2[VIV₆O₇?OH?₃{?OCH₂?₃CCH₂OH}₃] ?9H₂O,?NH₄?₃[VIV₆O₈?OH?₂{?OCH₂?₃CCH₃}₃],?NH₄?₃[VIV₆O₈?OH?₂{?OCH₂?₃CC₂H₅}₃]?3H₂O were synthesized by the new protocol and their structures were determined by single crystal X-ray diffraction,infrared spectroscopy and electrospray ionization mass spectrometry,while their optical and electrochemical properties were studied by UV spectroscopy and cyclic voltammetry.In further studies,the post-functionalization of H₂[VIV₃VV₃O₁₀{NH₂C?CH₂O?₃}₃]?10H₂O through amidation was explored and eleven new derivatives of mixed-valence polyoxovanadate were synthesized and structurally characterized.This work opens a new path to the rational design and controllable synthesis of mixed-valence POVs by the post-functionalization strategy.Futhermore,the products show versatile electrochemical properties in cyclic voltammetry studies and may have potential applications in catalysis and photoelectronic devices.