95Mo NMR study of the effect of structure on complexation of molybdate with alpha and beta hydroxy carboxylic acid ligands

Abstract

95 MoNMR study of the effect of structure on complexation of molybdate with alpha and beta hydroxy carboxylic acid ligands Abstract The utility of the quadrupolar, spin 5/2 95 Mo nucleus in NMR studies of complexation of molybdate have been demonstrated using model alpha hydroxyl carboxylic acids. The 95 Mo NMR spectra show a down field shift of the resonance upon complexation, presumably due to the smaller 1/∆E paramagnetic shift term for the octahedral molybdate complexes relative to the tetrahedral molybdate ion.The 95 Mo resonances are sufficiently distinct to establish three solution complexes for the reaction of lactic acid with molybdate. The effect of the structure of hydroxy carboxylic acids on complexation to molybdate (MoO4 2-) was studied with 13 C and 95 Mo NMR spectroscopy. The use of the NMR spectra of both nuclei © 2015. This manuscript version is made available under the Elsevier user license allows monitoring of the Lewis acidic molybdate site and the Lewis basic ligands.The beta hydroxy carboxylic acids, 3-hydroxypropanoic acid and salicylic acid,did not form complexes with molybdate, suggesting a preference for 5-membered chelated rings. The Lewis acidity of the negatively charged molybdate ion is rationalized with two schemes for the reaction with the chelating bidentate alphahydroxyl carboxylic acids.

Structure, stability, and properties of phenolic fibers modified by phenyl molybdate

“…The shift of the resonances of the phenoxy carbons to higher chemical shifts (158 ppm) are attributed to the electrophilic effect of molybdate groups reducing the shielding of the phenoxy carbons. 15 The broadened chemical shifts (152–158 ppm) of the phenoxy carbons illustrate that the molybdate groups entered the phenolic molecular chain.…”

8-Hydroxyquinoline-2-Carboxylic Acid as Possible Molybdophore: A Multi-Technique Approach to Define Its Chemical Speciation, Coordination and Sequestering Ability in Aqueous Solution

“…It is reported that, during complexation, Mo(VI) in molybdate often expands its coordination, usually from 4 (tetrahedral) to 6 (octahedral) [35]. Moreover, several structures have been reported in which strong binding, e.g., by catecholates or hydroxopyridinones, leads to MoO 3 and/or MoO 2 2+ moieties [36][37][38]: every oxygen atom from the original molybdate is "lost" during complexation through the formation of a water molecule that, from a mere stoichiometric point of view, corresponds to the involvement in the formation equilibrium of two protons per "lost" oxygen (of course they can be donated by the ligand itself).…”