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The results of electrocrystallising solutions of [M(S2C2(CN2)2] anions (where M = Ni, Pd or Pt) and BEDT-TTF or TMTSF are presented. The products of BEDT-TTF and the [M(S2C2(CN)2)2] anion are shown to be semiconductors.

We present results of transport measurements on the linear metal chain system Cs0.83[Pd(C2S2(CN)2)2].0.5H2O. The conduction band in this complex is formed by the overlap of the π-electron orbitals on the dithiolate ligands. Measurements were made under hydrostatic pressures up to 20Kbar and temperatures down to 1.2 K. At ambient pressure the system is semiconducting with a conductivity ∼5 S/cm and an activation energy ∼45 meV. On cooling the system undergoes several semiconductor-semiconductor phase transitions. With increasing pressure the activation energies of the two main phases decrease at 8meV/Kbar. Under a pressure of 18kbar the material is stabilised as a metal down to low temperatures and its resistance is still decreasing at 1.2 K. Thermopower measurements show the majority carriers to be holes for all phases.

Electrochemically prepared films of polypyrrole have been studied as electrode coatings in an electrochemical cell with potassium ferricyanide as the electroactive species in solution. The electrode-solution interface was studied by AC impedance measurements over the frequency range 0.003-105 Hz. A novel model circuit description of the electrode-electrolyte interface was devised, which consisted of seven elements (including a frequency-dependent Warburg impedance) for the bare platinum electrode and ten elements (including an additional Warburg impedance concerned with film oxidation and reduction) for the polypyrrole-coated electrodes. The values of the circuit element were calculated by computer fitting and excellent agreement was found between measured impedances and those predicted from the calculated circuit element values. Where parameters could be calculated from known physical properties of the system (e.g., the Warburg parameters) these agreed well with the fitted values. Model circuit element values were calculated for the bare platinum electrode and for polymer-covered electrodes for polypyrrole films of four different thicknesses. The most striking result is the large drop in the charge transfer resistance for the ferricyanide reaction when the electrode is covered with the polypyrrole film. The large drop in this value is partly explained by the increase in surface area (which from other parameters can be estimated to be 40-fold), but might additionally reflect electrocatalytic properties of the polypyrrole surface.

The electrical conductivity of the quasi-one-dimensional conductor ${\mathrm{Cs}}_{2}$[${\mathrm{Pt}{(\mathrm{CN})}_{4}]({\mathrm{N}}_{3})}_{0.25}$\ifmmode\cdot\else\textperiodcentered\fi{}0.5${\mathrm{H}}_{2}$O, CsCP(${\mathrm{N}}_{3}$), has been studied. Values for the intrachain band filling and electronphonon coupling as well as for the electronic interchain coupling are compared to those of the well studied tetracyanoplatinate complexes. The physical properties of CsCP(${\mathrm{N}}_{3}$) are explained from its structure and characteristic hydrogen bonding.

The variation of conductivity and thermopower with temperature for Rb 3 (H 3 O) 0.2 [Pt(CN) 4 ](O 3 SO·H·OSO 3 ) 0.5 ·0.8H 2 O is reported. The abrupt falls in conductivity at low temperature previously reported have been carefully studied and from the non-reproducible nature of the phenomena, it is deduced that these result from cracks in the sample rather than a phase change in the material.

Variable temperature (300-40 K) 4-probe d.c. conduction studies on Cs 2 [Pt(CN) 4 ](FHF) 0.39 and Rb 2 [Pt(CN) 4 ](FHF) 0.40 are described. In these salts T 3D occurs at a lower temperature than in K 2 [Pt(CN) 4 ]Br 0.3 ·3H 2 O and this is attributed to the absence of an inter-chain network of hydrogen bonded water molecules in the bifluorides.

The preparation, structure and solid state properties of Cs[Pd(S 2 C 2 (CN) 2 ) 2 ].0.5H 2 O are described. Although the structure shows the monoanions to exist as strongly bonded dimers the compound behaves as a small gap semiconductor with a conductivity of ≈ 5 Ω −1 cm −1 at room temperature. There is evidence of a transition to a wide gap semiconducting state around 240 K. K[Pd(S 2 C 2 (CN) 2 ) 2 ].H 2 O is a semiconductor at room temperature with a conductivity of 1 × 10 −2 Ω −1 cm −1 .

The crystal structures of K[Pd{S2C2(CN)2}2]·H2O and NH4[Pd{S2C2(CN)2}2]·H2O are described. The former has a structure consisting of an equidistant columnar stack of anions, whereas in the latter compound the anions are arranged as dimers in an eclipsed Pd over Pd arrangement.

A number of [Ni(S2C2(CN)2)2] monoanion salts of small cations have been prepared and their electrical conductivity and magnetic properties studied.

An investigation into the variation of the intensity of the satellite reflections with temperature in Zn 0.81 [Pt(C 2 O 4 ) 2 ]·6H 2 O is reported. The first appearance of satellites corresponds to a big fall in conductivity and a large change in the thermopower, even though the intensity of the satellites is quite weak. The phase transition from Cccm to Pccn space group results in the appearance of new satellites and further large changes in both conductivity and thermopower.

A new investigation of Vezes' red salt, first prepared in 1893 indicates that it should be reformulated as K2[Pt3(NO2)6O]·3H2O. Analytical, infrared, X-ray, and electrical-conductivity evidence suggests that the structure of the compound consists of planar anions arranged in a columnar stack resulting in the formation of linear chains of platinum atoms.

The preparation of the new 1-D conductors (NH4)1.169[Pt(C2O4)2][mddot]H2O (Am-OP) and [(CH3)2NH2]1.61 [Pt(C2O4)2] (DMA-OP) is described. The average intra-chain Pt-Pt separation is 2.82 A in Am-OP and 2.80 A in DMA-OP. The specific conductivity in the platinum atom chain direction is ˜50 Ω−1 cm−1 and ˜20 Ω−1 cm−1 for Am-OP and DMA-OP respectively. The variation of specific conductivity with temperature in the platinum atom chain direction is compared with that of other 1-D metallic complexes.

A preliminary study is presented on the AC impedance properties of polypyrrole covered platinum electrodes in contact with an aqueous electrolyte containing an electroactive species (K ferricyanide). AC impedance data have been measured over the frequency range 0.003 Hz – 100 kHz. A suitable circuit model to fit the data requires five resistive and five capacitative elements. Compared with a bare platinum electrode in contact with the same electrolyte solution, the polypyrrole covered electrode shows lower impedances in both real and imaginary parts over a wide range of frequencies. This is reflected in both lower values for the resistive circuit elements and higher values for the capacitative elements. The polypyrrole is clearly capable of charge storage, and in addition might be acting as a catalytic surface for the heterogeneous charge transfer reaction between the electrode and the electroactive species in solution.

Variable temperature (305−50K) 4-probe dc conduction and optical reflectivity (4,200 − 25, 000 cm−1 studies on Zn0.81[Pt(C2O4)2] · 6H2O are described. The optical properties are very similar to those of K2 [Pt(CN)4] Br0.3 · 3H2O except that ωp occurs at a lower frequency. The conduction properties are compared with those of the isostructural salts Co0.83 [Pt(C2O4)2] · 6H2O and Mg0.82 [Pt(C2O4)2] · 6H2O.

The crystal structures of [N(C2H5)4][Pt{S2C2(CN)2}2] and [H2O]x[NH4]1–x[Pt{S2C2(CN)2}2]·2 –xH2O are described. Both compounds contain anion dimers. In the former the dimer has a slipped configuration with Pt ⋯ S interactions whereas the latter contains the anions in an eclipsed configuration with a Pt over Pt arrangement. The difference in the structures is related to the size and nature of the cation. The electrical conduction and magnetic properties are related to the structures.

The crystal structure determination of the title compound (abbreviated as α-LiPt(mnt) has been performed at room temperature and 153 K. The [Pt(mnt)2]n− (mnt=1,2-dicyano-1,2-ethylenedithiolato, C4N2S22−) anions stack face-to-face along the c-axis with Pt···Pt distance of 3.6 A. The room temperature structure and the average structure of the 153 K superstructure are almost the same. The room temperature conductivity of α-LiPt(mnt) is about 200 S cm−1, and the compound undergoes a metal-insulator transition (Peierls transition) at 220 K. In α-LiPt(mnt) the conduction pathway is through the ligand-centered π-system which is composed of predominantly S 3pz orbitals. Oscillation photographs about the c-axis show strong satellite spots on the layerlines of (0.41+n)c* and (0.59+n)c* (n=0, ±1, ±2, ···) The content of Li cation reveals that these satellite spots can be described as 2kF spots. The regular appearance of characteristic satellite reflections indicates that α-LiPt(mnt) has a sinusoidally modulated latt...

The products obtained by crystallising [NH4]2[Pt(CN)4]Cl0.3·3H2O or K2[Pt(CN)4]Cl0.3·3H2O from solutions which contain high concentrations of chloride ions and protons have been studied. These products are shown to be isomorphous with the original compounds but contain extra chloride ions and protons in the lattice.

The X-ray crystal structure of NH4[Ni{S2C2(CN)2}2]·H2O has revealed that the planar [Ni{S2C2(CN)2}2]– anions form an eclipsed equidistant stack structure with a repeat distance of 3.918(8)A. At 98 K the repeat distance in the stack direction is double that at room temperature indicating that the anions are now associated as dimers. The room-temperature structure and low-temperature transition are related to the unusual magnetic properties of this compound.

A new partially oxidized bis(oxalato)platinate complex has been prepared which contains paramagnetic Co/sup 2 +/ counterions. The crystal and molecular structure of this new salt, Co/sub 0.83/(Pt(C/sub 2/O/sub 4/)/sub 2/).6H/sub 2/O, has been determined by single-crystal x-ray diffraction. The complex crystallizes in the orthorhombric space group Cccm with cell parameters of a = 14.379 (2) A, b = 16.501 (2) A, c = 5.682 (1) A, and Z = 4. Intensity data were collected on a Syntex P2/sub 1/ diffractometer for one octant out to a maximum 2 theta of 42/sup 0/ using Mo K..cap alpha.. x radiation. The structure was solved by Patterson methods and refinement led to final discrepancy indices of R(F/sup 2//sub 0/) = 0.029 and R/sub w/(F/sup 2//sub 0/) = 0.045. The structure consists of planar bis(oxalato)platinates stacked along the c direction with a Pt-Pt separation of 2.841 (1) A. The rotation angle between neighboring Pt(C/sub 2/O/sub 4/)/sup 1.66-//sub 2/ groups is 55.0 (3)/sup 0/. Each Co/sup 2 +/ ion is octahedrally coordinated to six water molecules, although these sites are only 83 percent occupied. Futhermore, we have located a completely occupied water site which is not within the coordination sphere of the Co/sup 2 +/more » ion. Since in all other respects Co/sub 0.83/(Pt(C/sub 2/O/sub 4/)/sub 2/).6H/sub 2/O and the structure of Mg/sub 0.82/(Pt(C/sub 2/O/sub 4/)/sub 2/).5.3 H/sub 2/O reported by Krogmann appear to be isostructural, we believe the magnesium salt may also contain this additional water site. Thermal gravimetric analysis of the cobalt salt has verified the degree of hydration is exactly 6.0.« less

The conductivity and dielectric constant at 35 GHz are reported for eight partially oxidised tetracyanoplatinate and bis (oxalato) platinate salts. Whenever possible the results are compared with those obtained from dc measurements.

Variable temperature (300–40K) 4-probe dc conduction studies on Cs 2 [Pt(CN) 4 ] Cl 0.30 are described. The results are compared with those of K 2 [Pt(CN) 4 ]Br 0.3○ 3H 2 O and Rb 2 [Pt(CN) 4 ] (FHF) 0.40 and the influence of the anion on T 3D is discussed.

The syntheses of vinylenedithiolethione (VDT-DTT) and its dimerised derivative bis(vinylenedithio)tetrathiafulvalene (BVDT-TTF) is reported as part of our studies on new synthetic pathways to planar extended S-donor ligands. These and other derived ligands have been discussed as materials for the synthesis of new organic conductors and one-dimensional metals.

The preparation of two series of 3,7-bis(dimethylamino)phenothiazin-5-ium (methylene blue, mb) salts with [M{S2C2(CN)2}2]2– and [M{S2C2(CN)2}2]–(M = Ni, Pd, Pt, or Cu) is described. Compressed pellets of all these compounds exhibit conductivities of less than 10–5Ω–1 cm–1 at room temperature. Single crystals of [mb][Pt{S2C2(CN)2}2] behave as semiconductors with an activation energy of 238 meV and a room-temperature conductivity of 10–5Ω–1 cm–1.

Interest in the structures and properties of low-dimensional metal complexes was stimulated by the work of Krogmann in the late 1960s.1 However the compounds which aroused so much interest then have a much longer history. Indeed many of the compounds that were studied intently in the 1970s were first prepared in the middle of the 19th century although the true nature of the materials was to remain a mystery for over a hundred years.

A series of new one-dimensional metals based on partially oxidised tetracyanoplatinate complexes containing both monovalent and divalent cations is described. The complexes appear to be isostructural with K2[Pt(CN)4]Cl0.3·3H2O but with ca. 13% of the cation sites containing a divalent cation and with all the halide sites occupied. The small change in composition is shown to have a large effect on the electrical conduction properties of the compounds because the effect of the introduction of divalent cations results in an increased stiffness of the lattice. This leads to a reduction of λ, the electron phonon coupling constant, resulting in increased conductivity at low temperatures.

The prototype 1D conductor K2Pt(CN)4Br0.3.3H2O(KCP(Br)) has been widely studied over the past eight years1. Although many theories have been proposed to explain the electrical conduction behaviour of this compound the importance and role of such effects as interchain coupling, partial 3D ordering of the lattice (Peierls transition) and the random potential of the halide ions, are still not understood. It has recently been shown that information about the importance of these effects can be obtained by studying an isomorphous series of compounds in which only one ion in the lattice is varied2.

U.v.–visible spectral studies show that in acetonitrile solution there is association between [Rh(CO)2(L–L)]+ or [Rh(CO)3(L–L)]+[where L–L = 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen)] cations and [RhX2(CO)2]–(where X = Cl or Br) anions. The extent of the interaction depends on L–L and X and is most pronounced for [Rh(CO)3(phen)]+ and [RhCl2(CO)2]–. The anion–cation compound formed by the reaction of L–L with [(OC)2Rh(µ-Cl)2Rh(CO)2] has been shown to be [Rh(CO)3(L–L)][RhCl2(CO)2]. All four compounds of the type [Rh(CO)3(L–L)][RhX2(CO)2] have been prepared in crystalline form by the action of CO on a solution of [Rh(cod)(L–L)][BPh4](cod = cyclo-octa-1,5-diene) and [RhX2(CO)2]– in 1,2-dichlorobenzene, a new preparative method.

The most novel features of partially oxidized tetracyanoplatinate (POTCP) complexes containing platinum atoms in a nonintegral oxidation state are their highly anisotropic physical properties. The structural basis for these properties is the stacking of square-planar tetracyanoplatinate, “TCP” = [Pt(CN)4], groups, 1, as illustrated in Figure 1. While many square-planar TCP salts of Pt2.0+ are known which form columnar stacks containing infinite chains of Pt atoms, e.g., Rb2[Pt(CN)4] · 1.5H2O, (intrachain Pt-Pt separation, d Pt-Pt is 3.42 A), 13 striking changes in these complexes can occur if the intrachain separation is ~ 3.0 A or less (d Pt-Pt in Pt metal = 2.78 A).66 These changes include the appearance of salts with brilliant metallic lusters ranging from copper to bronze to gold and the onset of quasi-one-dimensional (1-D) metallic conductivity. These properties arise from electron delocalization along the overlapped Pt 5d z2 orbitals (Figure 1) Measurements of the electrical conductivity parallel to the Pt chain reveal values which may be 105 greater than the conductivity perpendicular to the chain direction.

The X-ray crystal structure of NH4[Ni{S2C2(CN)2}2]·H2O has revealed that the planar [Ni{S2C2(CN)2}2]– anions form an eclipsed equidistant stack structure with a repeat distance of 3.918(8)A. At 98 K the repeat distance in the stack direction is double that at room temperature indicating that the anions are now associated as dimers. The room-temperature structure and low-temperature transition are related to the unusual magnetic properties of this compound.

The preparations, electrical conductivities, magnetic and spectroscopic properties of bis[cis-1,2-bis(trifluoromethyl)-1,2-ethylenedithiolato]nickelate, [Ni{S2C2(CF3)2}2]–, and bis[cis-1,2-bis(trifluoromethyl)-1,2-ethylenediselenato]nickelate, [Ni{Se2C2(CF3)2}2]–, salts with small counter ions are described.

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

The preparation and electrical conduction properties of a series of copper(II) salts of metal dithiolates are described. Compounds of the types Cu[M{S2C2(CN)2}2]2·2H2O (M = Ni, Pt, Pd, or Cu) and Cu [M{S2C2(CN)2}2]2·H2O (M = Ni, Pt, or Cu) all exhibit compressed pellet conductivities of > 10–6S cm–1 at room temperature.

The crystal structures of [N(C2H5)4][Pt{S2C2(CN)2}2] and [H2O]x[NH4]1–x[Pt{S2C2(CN)2}2]·2 –xH2O are described. Both compounds contain anion dimers. In the former the dimer has a slipped configuration with Pt ⋯ S interactions whereas the latter contains the anions in an eclipsed configuration with a Pt over Pt arrangement. The difference in the structures is related to the size and nature of the cation. The electrical conduction and magnetic properties are related to the structures.

It has been shown that substitution of small cations(e.g., alkali metal ions) for large bulky cations such as the tetra-n-butylammonium ion in salts prepared from the square planar complex, [X(mnt)2]−n, where (X — Ni, Pt, Pd; mnt — 1,2-dicyano-1,2-ethylenedithiolato), leads to a series of highly conducting materials1–6. Briefly, large bulky cations favor the alternate stacking arrangement (i.e., cation/anion/cation/anion/...) in the crystal structure which is an arrangement which is not highly conductive. On-the-other-hand, in some instances, the small cations appear to support segregated stacking patterns in which the square planar transition metal complex anions are stacked pancakewise and which is an arrangement which is much more conducive to high electrical conductivity. We report here an ESR study of a series of the platinum and palladium complexes based on small counterions. A goal of these studies is to better understand those physical properties which lead to better electrical conductivity. A preliminary report of our work on the Cs[Pd(mnt)2].O.5H2O is given reference 6.

The crystal structures of K[Pd{S2C2(CN)2}2]·H2O and NH4[Pd{S2C2(CN)2}2]·H2O are described. The former has a structure consisting of an equidistant columnar stack of anions, whereas in the latter compound the anions are arranged as dimers in an eclipsed Pd over Pd arrangement.

The preparation, and a detailed study of electrical conduction properties, of Li0.75[Pt(S2C4N2)2]·2H2O are described. The electrical conduction properties are compared with those of other one-dimensional metals.

Black needles of Lix[Pt(S2C4N2)2].2H2O (x ca. 0.75) exhibit a room temperature conductivity of 30–200 Ω–1 cm–1 and a temperature dependence of the conductivity similar to that of the one-dimensional metallic tetracyanoplatinate complexes such as K2[Pt(CN)4]Br0·3.3H2O.