Structural Characterization of a Nanocrystalline Inorganic−Organic Hybrid with Fiberlike Morphology and One-Dimensional Antiferromagnetic Properties
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- 作者：Igor Djerdj ; Minhua Cao ; Xavier Rocquefelte ; Radovan ern ; Zvonko Jaglii ; Denis Aron ; Anton Potonik ; Fabia Gozzo ; Markus Niederberger
- 刊名：Chemistry of Materials
- 出版年：2009
- 出版时间：July 28, 2009
- 年：2009
- 卷：21
- 期：14
- 页码：3356-3369
- 全文大小：1066K
- 年卷期：v.21,no.14(July 28, 2009)
- ISSN：1520-5002
文摘
A new nanocrystalline inorganic−organic hybrid compound, VO(C6H5COO)2 has been synthesized under solvothermal conditions by reacting vanadium(V) oxytriisopropoxide with benzoic acid in toluene. A detailed investigation of the composition, structure and properties of VO(C6H5COO)2 using chemical and thermal analysis, synchrotron X-ray powder diffraction, electron microscopy techniques including SEM, TEM and SAED, spectroscopy techniques like XPS, EDX and FTIR, SQUID magnetometry and EPR is carefully described. Due to the low-crystallinity of the final material, its crystal structure has been solved from synchrotron X-ray powder diffraction data by combining a direct space global optimization technique and DFT geometry optimization and subsequently refined by the constraint Rietveld method. The compound crystallizes in the monoclinic system with a = 20.652(3), b = 6.798(1), c = 9.954(1) Å, β = 92.145(6) °, space group C2, and Z = 4. The inorganic part of the structure can be regarded as staggered V−V−V chains, formed of corner-sharing VO6 octahedra, running along the monoclinic b-axis. A strong V−O bond alternation along the chain was evidenced by the DFT geometry optimization. The organic part is based on two crystallographically independent singly ionized benzoate moieties linked to vanadium atoms through a bidentate bridging mode. The morphology of VO(C6H5COO)2 exhibits long nanofibers, which further consist of smaller individual nanofibers aligned in parallel to the growth direction along the b-axis, as expected from the 1D nature of the compound. The magnetic susceptibility and X-band EPR measurements shows that the magnetic properties of VO(C6H5COO)2 can be described by a S = 1/2 linear antiferromagnetic chain model with the isotropic interaction between nearest neighbors and an estimated magnetic spin exchange parameter of J = −189 K. DFT calculations have also been carried out to simulate the optical response and to estimate the magnetic spin exchange related to VO(C6H5COO)2. Such calculations allowed explaining the yellow-green color of the powder and the one-dimensional character of the magnetic structure.