Andrea M. Hounslow

Correlations between nuclear magnetic resonance spectra and crystal structure. III. A13C nuclear magnetic resonance study in the solid state of bis(xanthato) complexes of mercury(II); The crystal and molecular structure of bis(n-propyl-dithiocarbonato)mercury(II)

The cross-polarization magic angle carbon-13 nmr spectra of a series of bis(xanthato) complexes of mercury(II) are reported; [Hg(S2COR)2]nR=Me, Et,nPr andiPr. The spectra correlate well with the known crystal structures of theR=Me, Et, andiPr compounds and with that of theR=nPr derivative for which a single-crystal X-ray diffraction study is also reported. The X-ray analysis of [Hg(S2COnPr)2]n shows that this compound adopts a two-dimensional structure comprised of connected 16-membered rings which arise as a result of bridgingn-propylxanthate ligands. The mercury atom lies on a crystallographic twofold axis of symmetry and exists in a distorted tetrahedral geometry with two unique Hg-S bond distances of 2.418(3) and 2.835(4) Å. Unit-cell dimensions for [Hg(S2COnPr)2]n are:a=7.371(3),b=8.534(4),c=11.618(4) A andZ=2 for the orthorhombic space groupP21212. The structure was refined by a full-matrix least-squares procedure to finalR=0.047 andRw=0.044 for 899 reflections withI≥2.5σ(I). While the solid state nmr spectra provide information on molecular (and crystallographic) symmetry they do not provide sufficient detail to enable structure determination for the [Hg(S2COR)2] compounds.

The inclusion of diflunisal by α- and β-cyclodextrins. A 19F Nuclear magnetic resonance and spectrophotometric study

The complexation of the diflunisal anion (DF) by α-cyclodextrin (αCD) and β-cyclodextrin (βCD) in aqueous solution at pH 7.00 at 298.2 K has been studied by 19F n.m.r. and u.v.-visible spectroscopy. The formation of 1:1 and 1:2 inclusion complexes by βCD proceeds through the two equilibria: [graphic omitted] characterised by K1=(1.81±0.20)× 105 dm3 mol–1 and K2=(3.07±0.25)× 103 dm3 mol–1. In the presence of αCD only the DF·αCD complex, characterised by K1= 17.0±0.9 dm3 mol–1, is detected.

Kinetic and equilibrium studies of the sodium(I) cryptates [Na.C211]+ and [Na.C21C5]+, and the sodium(I) diaza crown ether complex [Na.C21]+ in non-aqueous solution

Abstract To assess the effects of ligand structure and solvent size variation on the stability constants (K) and formation (kf) and decomplexation (kd) rate constants of the sodium(I) cryptates, [Na.C211]+ and [Na.C21C5]+, and the sodium(I) diaza crown ether complex, [Na.C21]+, (all of which possess the fifteen-membered 4,7,13-trioxa-1,10-diazacyclopentadecane ring as a common structural feature) have been studied in dimethylformamide (dmf), diethylformamide (def) and dimethylacetamide (dma) using potentiometric and 23Na NMR methods. For [Na.C211]+, [Na.C21C5]+ and [Na.C21]+ log K (dm3 mol−1) at 298.2 K=5.20, 2.87 and 2.10 in dmf; 5.10, 2.52 and 3.19 in def; and 4.74, 2.05 and 2.88 in dma respectively. For [Na.C211 ]+ kf (dm3 mol−1 s−1) and kd (s−1) at 298.2 K=1.92 × 106 and 12.1; 2.29×106 and 18.2; and 2.49×106 and 45.2 in dmf, def and dma respectively. For [Na.C21C5]+ in dmf kf=2.14×107 dm3 mol−1 s−1 and kd=2.88×104 s−1 at 298.2 K, but the exchange process is too rapid to come into the NMR timescale in the other two solvents, as is also the case for [Na.C21]+ in all three solvents. These results demonstrate the dominant effect of the fourth oxygen donor atom in C211 in greatly increasing the stability and decreasing the lability of [Na.C211]+ by comparison with those of [Na.C21C5]+ and [Na.C21]+. The variation in the molecular size of dmf, def and dma, which are of similar electron donating strength, has little effect on the stability and lability of the sodium(I) complexes studied.

Use of solid and gel state 13C NMR spectroscopy for differentiation between agarophytes and carrageenophytes

Both solid state (CP-MAS) and gel state (using standard solution state conditions) 13C NMR spectroscopy have been used to characterize a range of red algae that produce either agar or carrageenan. These techniques allow rapid determination of phycocolloid type within the algal tissue before extensive and time-consuming extractions and fractionations are carried out.

The inclusion of diflunisal by γ-cyclodextrin and permethylatedβ-cyclodextrin. A UV-visible and19F nuclear magnetic resonance spectroscopic study

AbstractThe complexation of the diflunisal anion (DF) by γ-cyclodextrin (γCD) and permethylatedβ-cyclodextrin (βPCD) in aqueous solution at pH 7.00 at 298.2 K, has been studied by UV-visible and19F NMR spectroscopy. The formation of 1∶1 and 1∶2 γCD inclusion complexes proceeds through the two equilibria:(K1)

Proton nuclear magnetic resonance study of N,N-diethylformamide exchange on (N,N-diethylformamide)2,2′2″-tris(dimethylamino)triethylamine)cobalt(II) and its copper(II) analogue

{\text{DF + }}\gamma {\text{CD}} \rightleftharpoons {\text{DF}} \cdot \gamma {\text{CD}}

A structural study of the complexation of the lithium ion by the cryptand 4,7,13-trioxa-1,10-diazabicyclo[8.5.5]icosane

(K2)