Studies of rare-earth stannates by sup 119 Sn MAS NMR. The use of paramagnetic shift probes in the solid state

Journal Article · Wed Jan 18 00:00:00 EST 1989 · Journal of the American Chemical Society; (USA)

DOI:https://doi.org/10.1021/ja00184a017· OSTI ID:5050721

Grey, C P; Dobson, C M; Cheetham, A K; Jakeman, R J.B. ^[1]

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1. Univ. of Oxford (England)

{sup 119}Sn MAS NMR spectra have been obtained from members of a series of rare-earth stannates Ln{sub 2}Sn{sub 2}O{sub 7} (Ln = La, Pr, Nd, Sm, Eu, Tm, Yb, Lu, and Y), all of which adopt the pyrochlore structure. Apart from La{sub 2}Sn{sub 2}O{sub 7}, Lu{sub 2}Sn{sub 2}O{sub 7}, and Y{sub 2}Sn{sub 2}O{sub 7}, these compounds are paramagnetic and exhibit a very large variation in {sup 119}Sn chemical shifts (from approximately +5,400 to {minus}4,200 ppm), which can be attributed principally to a Fermi contact shift mechanism. The spectra from the paramagnetic samples have large overall line widths associated with the substantial anisotropy of the shift, but the individual peaks within the spinning sideband manifolds remain sharp. Several tin pyrochlore solid solutions have also been studied (namely Y{sub 2-y}Ln{sub y}Sn{sub 2}O{sub 7} where Ln = Sm, Nd, Pr, and Eu and La{sub 2-y}Nd{sub y}Sn{sub 2}O{sub u}) by {sup 119}Sn MAS NMR. When the short relaxation times of nuclei close to paramagnetic centers were exploited, a series of peaks were observed, associated with the substitution of paramagnetic for diamagnetic lanthanide ions in the local coordination around a tin atom. For Y{sub 2-y}Sm{sub y}Sn{sub 2}O{sub 7} the composition of the solid solution could be determined from the intensities of these peaks. In the solid solutions the {sup 119}Sn nuclei were found to be sensitive not only to neighboring paramagnetic ions but also to paramagnetic ions in the second and third coordination spheres. The shifts induced in these cases arise primarily from a through-space dipolar pseudocontact mechanism and can be interpreted with a model for the site symmetry based on the crystal structure. 30 refs., 8 figs., 3 tabs.

• OSTI ID: 5050721
• Journal Information: Journal of the American Chemical Society; (USA), Vol. 111:2; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
EUROPIUM COMPOUNDS
PARAMAGNETISM
LANTHANUM COMPOUNDS
LUTETIUM COMPOUNDS
NEODYMIUM COMPOUNDS
PRASEODYMIUM COMPOUNDS
SAMARIUM COMPOUNDS
THULIUM COMPOUNDS
YTTERBIUM COMPOUNDS
YTTRIUM COMPOUNDS
EXPERIMENTAL DATA
NMR SPECTRA
TIN 119
DATA
DAYS LIVING RADIOISOTOPES
EVEN-ODD NUCLEI
INFORMATION
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
MAGNETISM
NUCLEI
NUMERICAL DATA
RADIOISOTOPES
RARE EARTH COMPOUNDS
SPECTRA
STABLE ISOTOPES
TIN ISOTOPES
TRANSITION ELEMENT COMPOUNDS
400201* - Chemical & Physicochemical Properties
400202 - Isotope Effects
Isotope Exchange
& Isotope Separation