Multicomponent polyanions. 41. Potentiometric and phosphorus-31 NMR study of equilibria in the molybdophenylphosphonate system in 0.6 M sodium (chloride) medium

Multicomponent Polyanions. 53. Structure of Tetrakis(trimethylammonium) Tetra-μ-oxo-bis(triaquahexadecaoxo(trioxophenylphosphato)hexamolybdate) Dihydrate, [NH(CH3)3]4[{(C6H5P)Mo6O21(H2O)3}2].2H2O

“…An earlier observation of a rapid exchange between the Mo 6 PhP and the Mo 7 PhP complexes on the 31 P NMR time scale indicated a close structural relationship between these complexes (Yagasaki et al, 1987 average OÐO distance of 2.89 A Ê (Matsumoto et al, 1975). On the other hand, a comparison between the present monomer and the third type mentioned above (Fig.…”

“…Each species is represented by an area and its fraction is represented by the area's vertical height at that pH. The curves have been calculated using the formation constants from the equilibrium analysis study (Yagasaki et al, 1987). Full drawn curves separate species which give different 31 P NMR resonances.…”

“…However, if the chemical formula of the polyanion in the crystal agrees with the composition obtained from the equilibrium analysis, it is likely that the structure in solution is analogous or closely related to that in the solid state. In a combined potentiometric and 31 P NMR equilibrium analysis of the three-component system H + ± MoO 2À 4 ±(C 6 H 5 P)O 2À 3 (Yagasaki et al, 1987), three different compositions of phenylphosphonatopolymolybdates were found; Mo 5 (PhP) 2 , Mo 6 PhP and Mo 7 PhP (C 6 H 5 P is designated PhP for simplicity). This speciation study was performed in a 0.600 M Na(Cl) medium, where [Na + ] was kept constant while [Cl À ] was allowed to vary.…”

“…1) and the formula was con®rmed to be (C 6 H 5 P) 2 Mo 5 O 4À 21 . The structures of the other two polyanions have so far only been proposed (Yagasaki et al, 1987). In order to determine the solution structures of the Mo 6 PhP and Mo 7 PhP species and to verify that Mo 2 (PhP) 2 in solution has the X 2 M 5 -type structure, a LAXS study on concentrated solutions has recently been performed (Lyxell et al, 1998).…”

Chiral Strandberg‐Type Molybdates [(RPO3)2Mo5O15]2− as Molecular Gelators: Self‐Assembled Fibrillar Nanostructures with Enhanced Optical Activity

“…[3,9] The interplay of these multiple ionic-type interactions is expected to control the solution self-assembly of the discrete POM units, as well as the surface mobility of the organic chelates and the morphology of the extended structures. [10,11] Density functional calculations, including relativistic and solvent effects, were performed to evaluate the impact of hydrogen bonding on the geometries and energies of the (R,R)-1 conformers in water. [11] The latter originate from rotation of the two protonated amino pendants, each of which acts as a monofunctional hydrogen-bond donor towards the Mo 5 O 15 multiple-acceptor surface according to the calculated electrostatic potential map (see Supporting Information).…”