TY - JOUR
T1 - Nanocomposite of a chromium Prussian blue with TiO2. Redox reactions and the synthesis of Prussian blue molecule-based magnets
AU - Holmes, Stephen M.
AU - Whelpley, Amy S.
AU - Girolami, Gregory S.
N1 - Funding Information:
We thank the Department of Energy (Grant DEFG02-96-ER45439) for support of this research through the Frederick Seitz Materials Research Laboratory at the University of Illinois at Urbana-Champaign.
PY - 2007/6/15
Y1 - 2007/6/15
N2 - The reaction of [NEt4]3[Cr(CN)6] with titanium(III) p-toluenesulfonate at a pH of 2 affords a gray solid whose metal content and spectroscopic and magnetic properties are fully consistent with it being a Prussian blue material of stoichiometry "TiIII[CrIII(CN)6] · H2O". The carbon, nitrogen, and hydrogen content, however, are not consistent with this stoichiometry, and further investigation showed that the gray material has a powder X-ray diffraction profile, infrared spectrum, and magnetic properties very similar to those of the "all-chromium" Prussian blue CrII[CrIII(CN)6]0.67 · 6H2O. All data, including the C, H, and N weight percentages, are consistent with the conclusion that the material isolated is a nanocomposite of CrII[CrIII(CN)6]0.67 · xH2O and TiO2 in the ratio of 1-1.6. These results suggest that TiIII reduces some of the [CrIII(CN)6]3- ions to generate TiIV and CrII; the former hydrolyzes to amorphous TiO2 · 2H2O, the latter loses its bound CN ligands and reacts with unreacted [CrIII(CN)6]3- ions to generate the crystalline all-chromium PB species. The electrochemical potentials suggest that the [CrIII(CN)6]3- ion should not be reduced by TiIII; evidently, this unfavorable reaction is driven by the insolubility of the reaction products. The results constitute a cautionary tale in two respects: first, that the characterization of Prussian blue materials must be conducted with care and, second, that the insolubility of Prussian blue analogues can sometimes drive reactions that in solution are thermodynamically unfavorable.
AB - The reaction of [NEt4]3[Cr(CN)6] with titanium(III) p-toluenesulfonate at a pH of 2 affords a gray solid whose metal content and spectroscopic and magnetic properties are fully consistent with it being a Prussian blue material of stoichiometry "TiIII[CrIII(CN)6] · H2O". The carbon, nitrogen, and hydrogen content, however, are not consistent with this stoichiometry, and further investigation showed that the gray material has a powder X-ray diffraction profile, infrared spectrum, and magnetic properties very similar to those of the "all-chromium" Prussian blue CrII[CrIII(CN)6]0.67 · 6H2O. All data, including the C, H, and N weight percentages, are consistent with the conclusion that the material isolated is a nanocomposite of CrII[CrIII(CN)6]0.67 · xH2O and TiO2 in the ratio of 1-1.6. These results suggest that TiIII reduces some of the [CrIII(CN)6]3- ions to generate TiIV and CrII; the former hydrolyzes to amorphous TiO2 · 2H2O, the latter loses its bound CN ligands and reacts with unreacted [CrIII(CN)6]3- ions to generate the crystalline all-chromium PB species. The electrochemical potentials suggest that the [CrIII(CN)6]3- ion should not be reduced by TiIII; evidently, this unfavorable reaction is driven by the insolubility of the reaction products. The results constitute a cautionary tale in two respects: first, that the characterization of Prussian blue materials must be conducted with care and, second, that the insolubility of Prussian blue analogues can sometimes drive reactions that in solution are thermodynamically unfavorable.
KW - Hexacyanometalate
KW - Hydrolysis
KW - Magnetic
KW - Nanocomposite
KW - Prussian blue
KW - Redox
KW - Titanium dioxide
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U2 - 10.1016/j.poly.2006.11.015
DO - 10.1016/j.poly.2006.11.015
M3 - Article
AN - SCOPUS:34249735402
SN - 0277-5387
VL - 26
SP - 2291
EP - 2298
JO - Polyhedron
JF - Polyhedron
IS - 9-11
ER -