New quasi-one-dimensional tetracyanidoplatinate, Cs4[Pt(CN)4](CF3SO3)2: Synthesis, structure, and physical characterization Original Research Article

The synthesis and some physical properties of a new quasi-one-dimensional tetracyanidoplatinate, Cs4[Pt(CN)4](CF3SO3)2 (CsCP(OTf)) are reported and described in comparison to the well-known K2[Pt(CN)4]Br0.30·3.2H2O (KCP). Single-crystal X-ray diffraction reveals Pt–Pt spacings to be greater than those of KCP by 5% longitudinal and 38% transverse, but much shorter than comparable spacings in other non-partially oxidized platinates. Anomalies are observed between temperatures 100 K and 200 K: (1) Longitudinal DC conductivity is two orders of magnitude higher and is non-monotonic with temperature, showing a minimum at around 170 K. (2) Nuclear magnetic resonance (NMR) longitudinal relaxation time T1 is at least three orders of magnitude higher than that of KCP, and is also non-monotonic with temperature, showing a sharp peak at around 120 K. Since X-ray diffraction reveals no structural transition at 120 K, these suggest a possible lattice freezing or stiffening at around 120 K.