Phase transformation in Y2[Pt(CN)4]3-21H2O

The great current interest in the chemical and physical properties of bis(oxalato)platinate salts can be directly traced to the characterization by Krogmann less than 20 years ago of several of these salts as partially oxidized materials with seemingly metallic-like properties in one dimension.1–4

Linear Chain Bis ( oxalato ) platinate Salts

Fits to the paramagnetic susceptibility of three mixed valency planar (MVP) compounds with columnar structure and one-dimensional metallic conduction properties reveal discontinuities in Curie constants for which no explanation is available. This discontinuity corresponds to a third-order phase transition, which is explained here as intrinsic and as associated with the lateral alignment of paramagnetic domain tips.



Die Anpassung an die paramagnetische Suszeptibilitat dreier planarer Valenz-Misch-Verbin-dungen (MVP) mit Spaltenstruktur und eindimensionalen metallischen Leitfahigkeitseigenschaften zeigt Diskontinuitaten der Curie-Konstante, fur die es keine Erklarung gibt. Diese Diskontinui-taten entsprechen einem Phasenubergang dritter Ordnung, der hier als intrinsisch erklart wird und mit der lateralen Reihung von paramagnetischen Domanenspitzen verknupft ist.

Paramagnetic domain tips in quasi-one-dimensional conductors

Mixed valence compounds exhibit a wide range of magnetic properties. These properties range from simple diamagnetism which is temperature independent and which may be estimated rather accurately from Pascal’s constants, to Curie-Weiss paramagnetism, to exceptionally complicated behavior which may arise from single ion effects, exchange coupling interactions, or both. Studies of the magnetic properties of mixed valence compounds often yield valuable information concerning the chemical nature and electronic structure of the substances. In this chapter, results ofrepresentative studies of magnetic properties of mixed valence compounds will be described with the aim of illustrating the phenomena which are exhibited and the manner in which the results are used in the solution of chemical problems. Systems of discrete clusters, chains, sheets, and three dimensional polymeric materials will be discussed here. For the most part, these will be compounds in which metal ions are bridged by ligands such as halides,oxide, pyrazine, and other ions and small molecules, although representative results for compounds containing metal-metal bonds will be included. Because of space limitations and a recent review on the subject, results on mixed valence metalloproteins and enzymes will not be covered.

H.S. Räde

Papers

Magnetic susceptibility of the one-dimensional conductor (H3O)1.6[Pt(C2O4)2]nH2O