Semiconductivity of Magnus' Green Salt Analogues

Abstract

IT has been suggested^1,2 that the chains of metal atoms found in the crystal lattices of many square planar d⁸ metal complexes might provide a path for electron transfer, detectable as semiconductivity. When reporting the polarized crystal spectra of Magnus' green salt (Pt(NH₃)₄PtCl₄, MGS) and its analogues¹, we briefly noted an attempt to measure the electrical conductivity of a single crystal of MGS from which it was concluded that the room temperature resistivity of the compound was extremely high. Since then two other measurements on MGS have appeared^3,4, which show that its conductivity is considerably higher than we suggested. In an effort to discover whether enhanced electrical conductivity is indeed associated with the presence of closely spaced metal atoms in this type of compound, we have now examined the range of substances related to MGS by replacement of the NH₃ with various alkylamines. It is known that such replacement both increases the Pt–Pt distance (ref. 2 and personal communication), and returns the visible and ultraviolet spectrum to a form more closely resembling that of K₂PtCl₄ (refs. 5 and 6). Our study confirms that MGS is an ohmic semiconductor and shows a clear relationship between conductivity and spectroscopic behaviour among the series of compounds.