Title Chemical composition of an aqueous oxalato-/citrato-$VO^{2+}$ solution as determinant for vanadium oxide phase formation Author Peys, Nick Maurelli, Sara Reekmans, Gunter Adriaensens, Peter De Gendt, Stefan Hardy, An Van Doorslaer, Sabine Van Bael, Marlies K. Faculty/Department Faculty of Sciences. Physics Publication type article Publication 2015 Easton, Pa , 2015 Subject Chemistry Source (journal) Inorganic chemistry / American Chemical Society. - Easton, Pa Volume/pages 54(2015) :1 , p. 69-78 ISSN 0020-1669 ISI 000347506500014 Carrier E Target language English (eng) Full text (Publishers DOI) Affiliation University of Antwerp Abstract Aqueous solutions of oxalato- and citrato-VO2+ complexes are prepared, and their ligand exchange reaction is investigated as a function of the amount of citrate present in the aqueous solution via continuous-wave electron paramagnetic resonance (CW EPR) and hyperfine sublevel correlation (HYSCORE) spectroscopy. With a low amount of citrate, monomeric cis-oxalato-VO2+ complexes occur with a distorted square-pyramidal geometry. As the amount of citrate increases, oxalate is gradually exchanged for citrate. This leads to (i) an intermediate situation of monomeric VO2+ complexes with a mix of oxalate/citrate ligands and (ii) a final situation of both monomeric and dimeric complexes with exclusively citrato ligands. The monomeric citrato-VO2+ complexes dominate (abundance > 80%) and are characterized by a 6-fold chelation of the vanadium(IV) ion by 4 RCO2- ligands at the equatorial positions and a H2O/R-OH ligand at the axial position. The different redox stabilities of these complexes, relative to that of dissolved O-2 in the aqueous solution, is analyzed via V-51 NMR. It is shown that the oxidation rate is the highest for the oxalato-VO2+ complexes. In addition, the stability of the VO2+ complexes can be drastically improved by evacuation of the dissolved O-2 from the solution and subsequent storage in a N-2 ambient atmosphere. The vanadium oxide phase formation process, starting with the chemical solution deposition of the aqueous solutions and continuing with subsequent processing in an ambient 0.1% O-2 atmosphere, differs for the two complexes. The oxalato-VO2+ complexes turn into the oxygen-deficient crystalline VO2 B at 400 degrees C, which then turns into crystalline V6O13 at 500 degrees C. In contrast, the citrato-VO2+ complexes form an amorphous film at 400 degrees C that crystallizes into VO2 M-1 and V6O(13) at 500 degrees C. E-info https://repository.uantwerpen.be/docman/iruaauth/3c05b5/0019758.pdf http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000347506500014&DestLinkType=RelatedRecords&DestApp=ALL_WOS&UsrCustomerID=ef845e08c439e550330acc77c7d2d848 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000347506500014&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=ef845e08c439e550330acc77c7d2d848 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000347506500014&DestLinkType=CitingArticles&DestApp=ALL_WOS&UsrCustomerID=ef845e08c439e550330acc77c7d2d848 Handle