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Supramolecular assemblies of ammonium ions (NH 4 + ) with crown ethers form a variety of NH 4 + (crown ether) supramolecular cation (SC + ) structures within the range of [Ni(dmit) 2 ] salts. A new pyramidal NH 4 + (12-crown-4) structure is found in the NH 4 + (12-crown-4) [Ni(dmit) 2 ] 3 (CH 3 CN) 2 salt. The SC + structures in the NH 4 + (crown ether)[Ni(dmit) 2 ] series vary from pyramidal-, sandwich-, to disk-shaped-structures with the crown ethers 12-crown-4, 15-crown-5, and 18-crown-6, respectively.

The salt [Na.15-crown-5][Ni(mnt)2].H2O has been prepared by electrocrystallisation and characterised by X-ray crystallography showing a stacking arrangement of [Ni(mnt)2]– and a slipped stack arrangement of the crown ethers.

The salt [Na.15-crown-5][Ni(mnt)2].H2O has been prepared by electrocrystallisation and characterised by X-ray crystallography showing a stacking arrangement of [Ni(mnt)2]- and a slipped stack arrangement of the crown ethers.

The X-ray structural analysis of the title compound revealed the formation of segregated [Ni(dmit)2] (dmit = 2-thioxo-1,3-dithiol-4,5-dithiolate) columns and dimeric K+2[PEG]2 (PEG = pentaethylene glycol) supramolecular cations in the crystal; the interaction between K+ and acyclic PEG was found to be weaker that that between K+ and cyclic polyether 18-crown-6.

The [NH 4 + ][Ni(dmit) 2 ] 3 complex, containing a macrocyclic molecule of 18-crown-6-ether (18C6), was obtained as [NH 4 + ][18C6][Ni(dmit) 2 ] 3 . This salt showed semiconducting behaviour with room temperature conductivity of 0.4 Scm −1 . The crystal is composed of segregated non-uniform stack of Ni(dmit) 2 and isolated ion-captured cavity of [NH 4 + ][18C6]. The NH 4 + ion was fully included in a cavity, and was tightly bounded through strong hydrogen bonds to the oxygen atoms of 18C6.

Phenyl-substituted Ni(dddt) 2 , Ni(phdt) 2 and Ni(dphdt) 2 , were synthesized and characterized by elemental analysis, FT-IR and UV spectroscopy. The ligand precursors were prepared by the [2+4] cycloaddition reaction between oligo(1,3-dithiole-2,4,5-trithione) and styrene or t -stilbene, respectively. [Ni(dphdt) 2 ] 1− shows rhombic esr g-values (g t = 2.099, g 2 = 2.039, g 3 =2.006) at 77K. It exhibits a cyclic voltamogram with a reversible oxidation potential at 0.34 V( vs. Ag/AgCl) and quasi- reversible one at −0.38V ( Δ V 1 2 =0.72 V ).

A bimetallic mercury(II) dithiolene complex in which the ligand exhibits three different modes of coordination to the mercury atoms within the same molecular species is reported.

The synthesis, electrochemical properties, preliminary electropolymerisation studies and the single-crystal X-ray crystal structure of the title compound 1 (TT-TTF), a novel thiophene-substituted tetrathiafulvalene electron donor, are described.

The synthesis and solution redox properties of the first diferrocenyl–dithiolene metal complex, bis(ferrocenylethylene-1,2-dithiolato) nickelate(II) are reported together with the X-ray crystal structure of the ligand precursor, 4-ferrocenyl-1,3-dithiole-2-one.

A novel dimeric penta-coordinated ion cavity of [Li + ] 2 [12-crown-4-ether] 3 has been formed in the highly conducting Ni(dmit) 2 salt. This salt showed a room-temperature conductivity of 30 S cm -1 and exhibited a semiconductor–semiconductor phase transition on the application of pressure or on lowering the temperature.

The charge transfer salts of newly synthesized donor thiadiazolo(ethylenedisulfanyl)diselenadithiafulvalene (DED) exhibit metallic behaviour down to low temperatures with a unique crystal structure and small SN distances in addition to an inter-chalcogen network.

Dianionic and neutral nickel complexes of substituted TTF dithiolate ligands have been prepared showing room-temperature conductivity of up to 10–1 S cm–1 for the neutral complexes; the crystal structure of the neutral complex [Ni(C10H10S8)2] is reported.

Dianionic mercury bis(tetrathiafulvalene dithiolate) complexes [NMe4]2[Hg(R2C6S8)2](R = Et or Bu) and the corresponding oxidised neutral complex [Hg(R2C6S8)2](R = Et) have been prepared. The crystal structure of [NMe4]2[Hg(R2C6S8)2](R = Et) has been determined and shows that the tetrathiafulvalene dithiolate units are tetrahedrally co-ordinated around the central Hg atom. Cyclic voltammetry and ESR studies indicated that there is very little interaction between the two ligands. A compressed pellet of the powdered neutral complex exhibited an electrical conductivity of 10–5 S cm–1 at room temperature.

The complex [N(C4H9)][Ni(diod)2] where diod = 1,4-dithia-6-oxa-2,3-dithiolate, has been prepared and structurally characterised. The complex crystallises in the space group l2/a with a= 16.890 A, b= 11.448 A, c= 18.382 A and β= 104.53°. The compound contains one unpaired electron per molecular unit and obeys the Curie–Weirs law over the temperature range 5–290 K with θ≈ 0. A charge-transfer salt of approximate composition [BEDT–TTF][Ni(diod)2]6 was prepared by electrocrystallisation and a compressed pellet of this salt had a room temperature conductivity of 10–2 S cm–1 and semiconducting behaviour over the temperature range 150–300 K.

Novel compounds and metal complexes containing both ferrocene and sulfur-based ligands have been prepared and their properties investigated. The reaction of [NEt4]2[Zn(C3S5)2] with (Chloromethyl)ferrocene led to the compound 4,5-bis(ferrocenylmethylsulfanyl)-1,3-dithiole-2-thione. Similarly, the reaction of the salt Cs2[C3OS4], led to the ketone analogue, 4,5-bis(ferrocenylmethylsulfanyl)-1,3-dithiole-2-one. The latter has been used to prepare a monoanionic tetraferrocenyl nickel dithiolene complex which shows an intense NIR absorption at 1250 nm recorded in CH2Cl2. Intermolecular coupling of the thione gave the novel tetra(ferrocenylmethylsulfanyl)tetrathiafulvalene electrochemical investigations of which revealed characteristic ttf and ferrocenyl redox processes. The single-crystal structure of this compound has also been determined.

Complexes of 3,4-toluenediamine, [M(tdi)2] where M = Ni, Pd or Pt, and 3,4-benzophenonediamine, [Ni(bpdi)2], have been synthesized and the value of χ(3) has been determined in DMSO at 1064 nm by the retroreflection DFWM technique. A value for χ(3) of 10.3 × 10–13 esu was observed for [Ni(bpdi)2] with a ratio of χ(3)xxxx/χ(3)xyyx, suggesting a non-linear process that is predominantly electronic.

A series of [NR4][M(dpdt)2](R = Bu, M = Ni 2, Au 3 or Cu 4; R = Me, M = Ni 5; H2dpdt = 6,7-dihydro-6-methylene-5H-1,4-dithiepine-2,3-dithiol) complexes have been synthesized. Magnetic susceptibility measurements indicate that the gold 3 and copper 4 complexes are diamagnetic, whilst the nickel salt 2 is paramagnetic over the temperature range studied (290–22 K). The solution redox properties are consistent with a 1,2-dithiolene structure for these compounds. Single crystal X-ray analysis on compounds 2–4 revealed crystal-packing structures consisting of two crystallographically independent [M(dpdt)2]– moieties possessing square-planar geometry, in which there are no intermolecular S ⋯ S contacts shorter than the sum of the van der Waals radii (3.70 A).

Three new nickel(II) complexes of 1-alkyl-2-phenyl asymmetrically substituted dithiolenes [Ni(SCR1CR2S)2](R1= Ph; R2= Bun, cyclopentylmethyl or 4-pentylcyclohexyl) have been prepared and their electrochemical properties and near-IR spectra studied. The crystal structures of the complexes in which R2= Bun or cyclopentylmethyl have been determined. The presence of bulky substituents adjacent to the ring has no affect upon the electrochemical or near-infrared properties. Third-order non-linear optical coefficients were measured by degenerate four-wave mixing.

The p-acetoxybenzylsulfanyl protecting group is compatible with the triethylphosphite mediated cross-coupling of 4,5-bis(alkylsulfanyl)-1,3-dithiol-2-ones, providing access to bis(protected)tetrathiafulvalenes, and thus to tetrathiafulvalenedithiolate dianion 10, which can be alkylated to give unsymmetrical tetrakis(alkylsulfanyl)tetrathiafulvalene derivatives.

The synthesis and characterisation of two new nickel bis(dithiolene) oligomers is described. The third-order non-linear optical index of refraction (n2) and real-to-imaginary ratio has been determined using the z-scan technique for one ditholene system as a guest in a poly(methylmethacrylate)(PMMA) host. A real-to-imaginary ratio (n2/β) of 4.3 was determined at a concentration of 5 × 1020 molecules cm–3.

The crystal structure of the title complex contains monoanion dimeric pairs in a staggered arrangement, in contrast to the structure reported for the corresponding dianion in which the anions are isolated.

The field of molecular metals and superconductors has developed rapidly since the first molecular metal was discovered in the late 1960s. The most extensive range of compounds are based on planar organic donor molecules containing sulfur or selenium atoms and complex metal anions containing multi-sulfur ligands. This review discusses the types of molecules involved and the relationship between the solid-state structures of these compounds and their conducting and superconducting properties.

The electrochemical behaviour of substituted ferrocene monomers and polymers was investigated using the techniques of cyclic voltammetry and pulse voltammetry at a platinum electrode. Both monomers and polymers obeyed the Hammett linear free-energy relationship between the half-wave potentials, E1/2, and the σ constants of the substituents. Normal pulse-voltammetric studies indicate that nearly all the ferrocene residues in the polymer are accessible to electron transfer in the electrode reaction. Diffusion coefficients calculated for substituted ferrocene polymers were in good agreement with those calculated using theoretical treatments.

The third-order optical non-linearity, χ(3), linear absorption coefficient, α, and the ratio of the real to imaginary parts of χ(3)have been measured at 1.06µm for a range of nickel dithiolene complexes with absorption bands between 0.77 and 1.06µm. From these data the non-linear retractive index, n2, and the device-based figure of merit, W(=Δnsat/αλ), were calculated. W was found to exceed 2 for materials with absorption maxima below 0.8–0.85µm. The non-linear refractive index of a poly(methyl methacrylate) host doped with 8 × 1019 molecules cm–3 of a nickel dithiolene was also measured and found to be nearly 2 × 10–9cm2 kW–1.

Conductivity data are reported for soluble co-polymers of aniline. The values for co-polymers are observed to be up to 106 times greater than those for the polymers derived from the co-monomers alone.

A simple one-step procedure is reported for the preparation of tetrakis(benzoylthio)tetrathiafulvalene (2) using octacarbonyldicobalt. The crystal structure of 2 is discussed and the preparation of some charge-transfer salts of 2 and their electrical conductivity has been determined. The use of 2 as a synthon for functionalised bis(ethylenedithio)tetrathiafulvalene derivatives is described.

Scanning tunnelling microscopy has been used in an attempt to determine the surface roughness of polypyrrole films, prepared by electrodeposition on platinum electrodes. Films of nominal thickness 0.7 and 15 µm were used and compared with bare platinum surfaces using both scanning tunnelling microscopy and conventional scanning electron microscopy. The surface area for the thicker polypyrrole films was found to be ca. 2.5 times that of the underlying platinum surface. This should be contrasted with our previous, much higher, estimate of this parameter (40) from electrochemical measurements (J. Phys. D, 20, 1411). This discrepancy is discussed in terms of the accessibility of internal spaces to electrochemically reactive species.

The crystal structure and electrical conductivities (including the effect of pressure) of [(CH3)4N][Pt(dmit)2]2(dmit = 4,5-dimercapto-1,3-dithiole-2-thione) have been studied. The Pt(dmit)2 anions form dimeric structures arranged as one-dimensional stacks along the [110] and [10] directions. A simple band-energy calculation indicates that the conduction band is formed by the HOMO band of Pt(dmit)2 owing to the strong dimeric nature of the molecular stacks.

Polypyrrole tetracyanoplatinate [PPPt(CN)4] has been prepared by the electrochemical polymerisation of pyrrole in aqueous K2Pt(CN)4. The polymer behaved as a semiconductor with a room-temperature conductivity of 17 S cm–1 and an activation energy of 9 meV between 270 and 110 K.The polymer films were exceptionally tough and exhibited good thermal stability. Films exhibited conductivities of 10–3 S cm–1 after heating in air to 310 °C and 10–2 S cm–1 after heating in argon to 550 °C.

Complexes of the ligand 1,2,5-thiadiazole-3,4-dithiol have been prepared; their spectroscopic and electrochemical properties show that they are potentially of use in preparing conducting materials.

The temperature dependences of the electrical conductivity of seven structurally similar quasi-one-dimensional anion deficient tetracyanoplatinates have been compared and discussed in terms of their chemical and structural properties. It is demonstrated that the variation from compound to compound of both the experimentally determined (κF, Δ) and calculated 1D parameters (ϵF, λ, Tp) can be understood in terms of the influence of the anions, cations, and water of hydration on the intra-chain PtPt distance and the degree of partial oxidation. The transverse electron coupling constant, ν, is calculated using the experimentally determined 3D ordering temperature T3D, and is also shown to be dependent on the constituents of the crystal lattice.

The crystal structures, superstructures, dc conductivity, optical properties, and thermopower of six linear-chain conductors of the type M0.8[Pt(C2O4)2]⋅(M=Ni,Co,Zn,Fe,Mg,Mn), where M is a divalent metal (M=Ni,Co,Zn,Fe,Mg,Mn), have been studied. At high temperatures they form a common orthorhombic metallic phase (I) with conductivities of 30–200 (Ω cm)-1 and thermopowers of 5–10 μV/K, with the lattice weakly modulated by the one-dimensional Peierls distortion. Below T1, three compounds (Ni,Co,Zn) form a semiconducting phase (A-II) due to the ordering of the [M(H2O)6]+2 cations. As the cation superlattice is commensurate with the three-dimensional Peierls distortion, these salts transform at a lower temperature T2 into a charge-density-wave phase (A-III). In the other three compounds (Fe,Mg,Mn), the cations order in a superlattice (phase B-II) which is incommensurate with both the average Pt-ion lattice and the three-dimensional Peierls distortion, and therefore no charge-density-wave state is formed. The influence of competing interactions is briefly discussed.

The preparation, crystal structure, and electrical conduction properties of Rb[Pt{S2C2(CN)2}2]·2H2O are described. The planar anions are arranged in a dimeric eclipsed configuration to form a columnar stacked structure. The room-temperature conductivity in the platinum atom chain direction is 2.5 ×10–5Ω–1 cm–1 and the compound behaves as a semiconductor.

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.

Further work on the chemical composition of the one-dimensional metallic metal dithiolene complex Li-Pt(mnt) is reported. The electrical conduction and thermopower properties of the nickel and palladium complexes are reported and compared with those of the platinum compound.

Variable temperature (300–40K) studies at 35 GHz on Co 0.83 Pt ( C 2 O 4 ) 2 . 6H 2 O are described. The conductivity in the platinum atom chain direction is found to be frequency independent above ∼250K but frequency dependent below this temperature. e1 is found to be ∼150 and almost temperature independent in the range 40–110K.

X-ray studies of the quasi-one-dimensional conductor Co0.83 [Pt(C2O4)2]·6H2O, Co(def)OP, show both a Peierls distortion with a period of 2k F = 1.70·2π/c and a separate (earlier reported) three-dimensional superlattice. The two distortions couple, so that the drastic decrease in electrical conductivity is accompanied by the occurence of the superlattice spots with a common critical temperature, T = (297 ± 4)K. The striking differences between Co(def)OP and Mg(def)OP are discussed and explained in terms of the different atomic structures of the cations.

The X-ray structural and electrical properties of some cation radical salts of the type D n X [where D=ethylenedithiotetrathiafulvalene (EDTTTF), pyrazinoethylenedithiotetrathiafulvalene (PEDTTTF), methylenedithiotetrathiafulvalene (MDTTTF), pyrazinoethylenedithiodiselenadithiafulvalene (PEDTDSDTF), ethylenedithiodiselenadithiafulvalene (EDTDSDTF), [4,5-b] pyridinodithiotetrathiafulvalene ([4,5-b]PEDTTTF), dimethylethylenedithiotetrathiafulvalene (DMEDTTTF), bis(ethylenedithio) tetrathiafulvalene (BEDTTTF); X=I 3 , IBr 2 , AuI 2 , BF 4 , ClO 4 , PF 6 , etc; n=1,2…] were studied.

A study of the formation of thin electrically conducting films of PVC and ABS containing 1 – 4% of organic charge-transfer salts is described. It was found to be impossible to prepare conducting films of epoxy resins containing the same charge-transfer salts because of the chemical action of the curing agents on the organic salts.

Four different crystalline phases of Zn0.81[Pt(C2O4)2].6D2O have been observed and partially characterized by single crystal neutron diffraction measurements. A crystal in the previously reported orthorphombic α-form was pulled along its c-axis at room temperature and was found to transform to a monoclinic β-form. Two new coexisting phases, monoclinic γ-Zn-OP and orthorhombic δ-Zn-OP were found when the sample was cooled to 200 K. Further crystallographic work is necessary in order to establish the detailed nature of the new phases.

X-ray diffuse scattering studies at room temperature for seven one-dimensional metallic complexes are reported. The crystal structure and the temperature dependence of both the electrical conductivity and X-ray diffuse scattering for Rb3(H3O)02 [Pt(CN)4] (O3SOHOSO3)050.8H2O are reported and related to the development of a non-Peierls superstructure below room temperature. The Rb complex is unique in that it contains a polyatomic (> 2) trianion and a ratio of three alkali metal ions per Pt atoms instead of the usual two.

Fundamental structure, kF and 2kF satellite reflections, and electrical properties of Ni0.84[Pt(C2O4)2]·6H2O (Ni–OP) were determined. Complex Ni–OP crystallizes in the orthorhombic space group Pccn with cell parameters of a=14.296(2), b=16.387(3), and c=5.671(1) A and Z=4. Ni–OP is essentially isostructural with Mg–OP (Mg0.82[Pt(C2O4)2]·5.3H2O) and Co–OP (Co0.83[Pt(C2O4)2]·6H2O). The space group of Mg–OP and Co–OP is Cccm. Owing to the change in the space group, there are two independent Pt chains in Ni–OP. X-Ray studies of M–OP (M=Co, Ni) show that there exist strong kF satellite spots and weak 2kF spots. One M2+ cation is vacant per period of the lattice modulation wave of the platinum chain, λ2kF. The periodic cation defect induces the kF modulation waves. The 2kF waves do not have a Peierls origin but are induced by the kF modulation wave. A second order phase transition is observed at about 305 K above which the 2kF spots disappear.

The complexes Cs[PtX3(NO2)(NH3)] (where X = Br or I) have been shown by photoelectron spectroscopy, optical and X-ray studies to be Class II halogen-bridged mixed valence compounds. They behave as semiconductors between 0 and 60°C and their electrical conduction properties are compared with those of other mixed valence complexes of platinum.

The X-ray crystal structure analysis of Li0.5[Pt(mnt)2]·2H2O (mnt= 1,2-dicyanovinylene-1,2-dithiolato, C4N2S22−) has revealed that the [Pt(mnt)2]0.5− anions are stacked face-to-face along the a-axis to form a fourfold platinum chain. In contrast to the regular chain in the metallic compound Li0.8[Pt(mnt)2]·2H2O, the fourfold structure can be regarded as a Peierls insulating structure. The room temperature conductivity is about 1 S cm−1.

The main structural findings reported here, which bear on the diminished electrical conductivity of (NH/sub 4/)/sub 2/(Pt(CN)/sub 4/)Cl/sub 0/./sub 3/ . 3H/sub 2/O compared to prototype K/sup 2/(Pt(CN)/sub 4/)Br/sub 0/./sub 3/ . 3H/sub 2/O, are that while the intrachain Pt-Pt spacings are shorter and are of equal length (2.88(1)A) in the K+ salt, they are longer and are of different length (2.910(5) and 2.930(5)A x rays) in the NH/sub 4//sup +/ salt. Thus the formation of alternately long and short Pt-Pt separations (dimerization) in NH/sub 4/CP(Cl) is likely one of the most important factors contributing to its electrical conduction properties. A factor which supports hypothesis is that in RbCP(Cl), the Pt-Pt distances are also of unequal length (2.924(8) and 2.877(8)A), and Rb CP(Cl) has lower room temperature conductivity than KCP(Br). The complete explanation for the structure-conductivity relationships in those POTCP complexes is obviously much more complicated, because although a Rb/sup +/ ion has nearly the same cation radius as NH/sub 4//sup +/ and RbCP(Cl) and NH/sub 4/CP(Cl) are isostructural, the low-temperature electrical conductivity (NH/sub 4/CP(Cl)<< RbCP(Cl)) is vastly different.