Investigation of layered double hydroxides intercalated by oxomolybdenum catecholate complexes
authors Monteiro, B; Gago, S; Paz, FAA; Bilsborrow, R; Goncalves, IS; Pillinger, M
nationality International
journal INORGANIC CHEMISTRY
keywords CAMBRIDGE STRUCTURAL DATABASE; DIFFRACTION BEAM LINE; CURVED-WAVE THEORY; POWDER DIFFRACTION; CRYSTAL-STRUCTURE; X-RAY; EXAFS CALCULATIONS; DICHOTOMY METHOD; ANION-EXCHANGE; MOLYBDENUM
abstract Oxomolybdenum(VI) complexes of 3,4-dihydroxybenzoic acid (3,4-H(2)dhb) have been incorporated into layered double hydroxides (LDHs) by treatment of the LDH-nitrate (Zn-Al, Mg-Al) or LDH-chloride (Li-Al) precursors with aqueous or water/ethanol solutions of the complex (NMe4)(2)[MoO2(3,4-dhb)(2)]center dot 2H(2)O at 50 or 100 degrees C. The texture and chemical composition of the products were investigated by elemental analysis and scanning electron microscopy (SEM) with coupled energy dispersive spectroscopy (EDS). Microanalysis for N and EDS analysis for Cl showed that at least 90% of nitrate or chloride ions were replaced during the ion exchange reactions. The final Mo content in the materials varied between 6.5 and 11.6 wt%. Mo K-edge EXAFS analysis, supported by IR, Raman, UV-vis, and C-13{H-1} CP/MAS NMR spectroscopic studies, showed the presence of cointercalated [MoO2(3,4-dhb)(2)](m-) and [Mo2O5(3,4-dhb)(2)](m-) complexes in proportions that depend on the type of LDH support and the reaction conditions. The binuclear bis(catecholate) complex, with a Mo center dot center dot center dot Mo separation of 3.16 angstrom, was the major species intercalated in the Zn-Al and Li-Al products prepared using only water as solvent. The X-ray powder diffraction (XRPD) patterns of all the Mo-containing LDHs showed the formation of an expanded phase with a basal spacing around 15.4 angstrom. High-resolution synchrotron XRPD patterns were indexed with hexagonal unit cells with a c-axis of either 30.7 (for Li-Al-Mo LDHs) or 45.9 angstrom (for a Zn-Al-Mo LDH). Fourier maps (F-obs) calculated from the integrated intensities extracted from Le Bail profile decompositions indicated that the binuclear guest species are positioned such that the Mo -> Mo vector is parallel to the host layers, and the overall orientation of the complex is perpendicular to the same layers. The thermal behavior of selected materials was studied by variable-temperature XRPD, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC).
publisher AMER CHEMICAL SOC
issn 0020-1669
year published 2008
volume 47
issue 19
beginning page 8674
ending page 8686
digital object identifier (doi) 10.1021/ic800420a
web of science category Chemistry, Inorganic & Nuclear
subject category Chemistry
unique article identifier WOS:000259603800038
  ciceco authors
  impact metrics
journal analysis (jcr 2019):
journal impact factor 4.825
5 year journal impact factor 4.501
category normalized journal impact factor percentile 92.222
dimensions (citation analysis):
altmetrics (social interaction):



 


Sponsors

1suponsers_list_ciceco.jpg