Spectroscopic and ESR studies of Cd₂P₂S₆ intercalated with pyridine complexes of ferric ion

Cd₂P₂S₆ crystallizes in a layered structure which is readily intercalated with a variety of Lewis bases. We have studied the intercalation reactions of this lattice with pyridine complexes of several transition metal ions and Ce⁴⁺. In some instances (e.g. Mn²⁺) the metal ion could be co-intercalated with pyridine with little or no effect on the distribution of reaction products formed within the van der Waals gap. However, certain transition metal ions had a dramatic effect on the product distribution obtained. Co-intercalation of Fe³⁺, for example, results in the production of a highly colored polysulfide species within the van der Waals gap. The intercalated species were identified by mass spectroscopic analysis during thermal de-intercalation. The co-intercalated paramagnetic transition metal ions are useful as ESR spin-probes for the study of the structure and dynamics of the intercalate layer. Analysis of the ESR spectra indicate that co-intercalated Mn²⁺ can enter Cd²⁺ lattice vacancies at elevated temperatures.