Electron nuclear double resonance study of pure and aquated rhodium complexes in silver chloride emulsions

Citation
Td. Pawlik et al., Electron nuclear double resonance study of pure and aquated rhodium complexes in silver chloride emulsions, J PHYS-COND, 10(50), 1998, pp. 11795-11810
Citations number
19
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
JOURNAL OF PHYSICS-CONDENSED MATTER
ISSN journal
09538984 → ACNP
Volume
10
Issue
50
Year of publication
1998
Pages
11795 - 11810
Database
ISI
SICI code
0953-8984(199812)10:50<11795:ENDRSO>2.0.ZU;2-2
Abstract
Detailed information has been obtained on the structure of pure and aquated Rh2+ complexes in AgCl using multifrequency EPR and powder ENDOR spectrosc opy. Because of the anisotropy of the Rh2+ centre g matrix it was possible to selectively excite Rh2+ centres with a specific angle between the z axis of the g matrix and the magnetic field axis. As a result, almost single-cr ystalline-like ENDOR spectra were obtained and the angular dependence of th e ENDOR spectra could be obtained by scanning the magnetic field over the r ange of the Rh2+ EPR spectra. Three different Rh2+ centres were detected th at are distinguished by different thermal stabilities, different parameters of the g matrix and the hyperfine matrices of the central Rh nucleus and l igand H, Cl and Ag nuclei. A pure Rh2+ centre without H2O ligands could onl y be generated in an emulsion where great care was taken to prevent the aqu ation of the [RhCl6](3-) dopant ion in the dopant solution and during the p recipitation. This centre had the highest thermal stability. In an emulsion prepared conventionally two Rh2+ centres were found that are associated wi th one and two H2O ligands bound to the Rh2+ ion in the plane perpendicular to the g matrix z axis. Using the results of the EPR and ENDOR analysis in combination with the results of a total energy calculation two models are proposed that contain the positions of the H2O ligands and the charge compe nsating vacancies.