Orientation et dynamique moléculaire de sondes paramagnétiques en phase lamellaire dibutylephosphate de sodium/eau

Abstract

R e~u le 24 mai 1983' C. CHACHATY. Can. J. Chem. 62, 1246Chem. 62, (1984. Les solutions aqueuses de dibutylephosphate de sodium (NaDBP) en concentrations de 3 a 4 mol L--' forment, entre 280 et 340 K , une phase cristalline liquide lamellaire. On Ctudie par rpe I'orientation ct la dynamique moltculaire dans cette phase, de sondes paramagnktiques telles que I'ion vanadyle et les radicaux nitroxydes, tempoamine, tempone et tempobutanamide.L'ion V02+ forme, avec le groupe phosphate, un complexe dont I'axe magnttique z est orient6 en moyenne selon la normale au plan lamellaire. La mobilitd moltculaire h i'interface entre les couches d'eau et de DBP-est donnCe par le temps de corrClation de nutation de I'axe z que I'on dtduit de la largeur totale du spectre par la relation empirique TR = a[I -(AII/Axx)I1'. Les parametres a = 2,95 X lo-" s et b = -1,42 sont dttermints par des mesures en fonction de la viscositd, des largeurs de raies et de l'anisotropie du couplage hyperfin de vO" La tempoamine et la tempone se localisent dans les domaines polaires de la mCsophase avec une reorientation rapide autour de la direction N-0 orientte en moyenne selon le directeur de la phase lamellaire. L'anisotropie de rkorientation de ces radicaux est attribuable selon les cas h la formation de liaisions hydrogene avec les groupes phosphates ou les molCcules d'eau interstitielles. On Ctablit quelques corrClations entre la rpe de ces sondes paramagnttiques et la rmn de ' H et "P des molCcules de substrat.C . CHACHATY. Can. J. Chem. 62, 1246 (1984). Aqueous solutions of sodium dibutylphosphate (NaDBP) give rise to lamellar liquid crystalline phase between 280 and 340 K for NaDBP concentrations ranging from 3 to 4 mol L-'. The orientation and dynamic behaviour of several paramagnetic probes such as the vanadyl ion, tempoamine, tempone and tempobutanamide dissolved in this phase have been investigated by esr.The vanadyl ion binds to the phosphate group, forming a complex. the z magnetic axis of which is on the average perpendicular to the lamellar plane. The molecular mobility at the H20/DBP-interface is given by the reorientation correlation time of the z axis, which is derived from the total width of the spectrum, using the empirical relation rR = a[1 -( A~~/ A~) ]~. The parameters a = 2.95 X lo-" s and b = -1.42 are obtained from the viscosity dependence of the esr line widths and of the anisotropic hyperfine couplings.The tempone and tempoamine are localized in the polar domains of the mesophase, reorienting rapidly about the N-0 direction which is, on the average, parallel to the director of the lamellar plane. The anisotropic motion of these radicals is assigned to hydrogen bonding which occurs, according to the cases, with water molecules or phosphate groups. Some correlations are established between the esr of spin probes and ' H and "P nmr experiments on substrate molecules.

Electron paramagnetic resonance study of the physical gelation of a copper complex in cyclohexane

“…4) are 4.8 x 10-11 s and - 1.6 respectively. These values are comparable to those obtained for instance for vanadyl acetyl-acetonate under similar conditions [29].…”

Studies of Cetylpyridinium Chloride and Cetylpyridinium Salicylate in Solution and Adsorbed on Silica Surfaces Using X- and W-Band Electron Paramagnetic Resonance Spectroscopy

“…Our g values are most directly comparable to those from previous work on amino-TEMPO, which is the TEMPO headgroup with an amine rather than a quaternary amine. For this spin probe, Chachaty reported a g matrix of g xx = 2.0098, g yy = 2.0062, and g zz = 2.0026 which is similar to our values. Ottaviani et al reported g xx = 2.0097, g yy = 2.0063, and g zz = 2.0035 for trimethyl-tempamine, which is HTAB* with the hexadecyl group replaced by a methyl group.…”

Preparation of Some Homologous TEMPO Nitroxides and Oxoammonium Salts; Notes on the NMR Spectroscopy of Nitroxide Free Radicals; Observed Radical Nature of Oxoammonium Salt Solutions Containing Trace Amounts of Corresponding Nitroxides in an Equilibrium Relationship

“…They were prepared by well-known reactions , and were compared with TEMPO itself and TEMPO nitroxides. Nitroxides 1c and 1d have been previously prepared and studied for their EPR properties. − …”