Thallium(III) coordination compounds: chemical information from Tl-205 NMR longitudinal relaxation times
2002 (English)In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 40, no 11, 716-722 p.Article in journal (Refereed) Published
Tl-205 longitudinal relaxation rate measurements were performed on several thallium(III) complexes with the composition Tl(OH)(n)(H2O)(6-n)((3-n)+) (n = 1,2), Tl(Cl)(n)(H2O)(m-n)((3-n)+), Tl(Br)(n)(H2O)(m-n)((3-n)+) (m = 6 for n = 1-2, m = 5 for n = 3, m = 4 for n = 4), Tl(CN)n(H2O)(m-n)((3-n)+) (m = 6 for n = 1-2, m = 4 for n = 3-4) in aqueous solution, at different magnetic fields and temperatures. C-13 and D-2 isotopic labelling and 114 decoupling experiments showed that the contribution of the dipolar relaxation path is negligible. The less symmetric lower complexes (n < 4) had faster relaxation rate dominantly via chemical shift anisotropy contribution which depended on the applied magnetic field: T, values are between 20 and 100 ms at 9.4 T and the shift anisotropy is &UDelta;σ = 1000-2000 ppm. The tetrahedral complexes, n = 4, relax slower; their T-1 is longer than 1 s and the spin-rotation mechanism is probably the dominant relaxation path as showed by a temperature dependence study. In the case of the TICl4- complex, presumably a trace amount of TICl52- causes a large CSA contribution, 300 ppm. Since the geometry and the bond length for the complexes in solution are known from EXAFS data, it was possible to establish a correlation between the CSA parameter and the symmetry of the complexes. The relaxation behaviour of the Tl-bromo complexes is not in accordance with any known relaxation mechanism.
Place, publisher, year, edition, pages
2002. Vol. 40, no 11, 716-722 p.
NMR, Tl-205 longitudinal relaxation, aqueous solution, thallium halide complexes, thallium cyanide complexes, spin-lattice relaxation, acidic aqueous-solution, equilibrium dynamics, magnetic-resonance, cyanide complexes, exchange, system, c-13, spectroscopy, bromide
IdentifiersURN: urn:nbn:se:kth:diva-21993DOI: 10.1002/mrc.1077ISI: 000178816300005OAI: oai:DiVA.org:kth-21993DiVA: diva2:340691
QC 201005252010-08-102010-08-10Bibliographically approved