ESR studies of inter- and intra-lamellar cation exchange processes in Cd2P2S6

Abstract

The transition metal chalcogenides, M, P2S1 (M = divalcnt transition metal cation), are lamellar materials that undergo an unusual cation exchange process when their crystals are placed in contact with a solution of a transition metal salt. EPR spectroscopy has been used to examine the exchange of paramagnetic Co2 + for Cd*+ in diamagnetic CdrP,S,. It has been possible to study the uptake of ions by the lamellar lattice and to examine the cation coordination environment through its effect on the parameters of the spin-Hamiltonian. In order to extract details of the Co2+ coordination from the observed EPR spectra, theoretical values of the g-value have been computed as a function of several crystal field parameters. The results for Co'+ are compared with previous results for the insertion of Mn'+ into Cd,P2S6 by cation exchange. The relative occupancy of the inter-and intra-lamcllar sites is a function of the cation type and the solvent employed.

Physical properties of new ordered bimetallic phases M0.25Cd0.75PS3 (M = ZnII, NiII, CoII, MnII)

“…6). Similar behaviour has been reported for other Co II containing phases 24 . The spectrum is consistent with Co II ions in a trigonally distorted octahedral environment 24 , due to the insertion of these cations in the vacancies of K0.5Cd0.75PS3.…”

“…Similar behaviour has been reported for other Co II containing phases 24 . The spectrum is consistent with Co II ions in a trigonally distorted octahedral environment 24 , due to the insertion of these cations in the vacancies of K0.5Cd0.75PS3. It is evident that hyperfine structure is not present in these spectra and to account for the physical mechanism we hypothesize that the Co II ions are coupled among themselves by strong exchange interactions.…”

“…It is possible to change the chalcogenide, obtaining phases with sulfur and selenium, and it is possible to replace the transition metal ion. Many combinations of transition metal ions have been used, 3d II -3d II21,22 , 3d II -4d II23,24 , or combination with 3+ cations, such as aluminium, gallium, indium have been reported 25 . Lanthanide(III) ions have also been involved in some heteronuclear phases, combined with sodium or potassium ions 26,27 .…”

Theoretical investigations of the local structure and the EPR parameters for the trigonal Co2+ center in K4CdCl6

“…[7] seems astonishing. The reason may be adoption of the incorrect relationship between the signs of Dg and Db; i.e., when Db > 0; Dg > 0; and when Dbo0; Dgo0 [33]. This incorrect relationship usually arises from misassignment of the lowest state ( 4 A 2 or 4 E).…”

Crystallization of Anderson−Evans Type Chromium Molybdate Solids Incorporated with a Metal Pyrazine Complex or Coordination Polymer

“…Thus, for 8 and 10 , one anticipates a C value of 2.12 and 1.80 emu/mol, respectively, in reasonable agreement with measured values. For 7 , Co 2+ (3d 7 ) in octahedral coordination becomes split by the crystal field into an effective spin S = 1 / 2 and g ∼ 4.4, , yielding an expected C value of 3.69 emu/mol. Tetragonal distortions to the octahedra give rise to an anisotropic g tensor with components g ∥ and g ⊥ , yielding an effective value of g 2 = 1 / 3 ( g ∥ 2 + 2 g ⊥ 2 ).…”