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The bimetallic complex (NBu4 +)2{C2S4[NiS2C2S2(CO)]2}2− has been prepared and its X-ray crystal structure has been determined. The anions are packed in layers parallel to the crystallographic (0 1 0) plane and are intermingled with parallel layers of closely packed cations. The geometry of the C2S4 (tetrathiooxalate, tto) moiety in the title compound is intermediate between that in tto4− and tto2− systems. The solution electrochemistry reveals the reversible formation of the monoanionic species and the irreversible formation of the neutral species (or a species possessing a nonintegral oxidation state). Conducting salts have been obtained by complexation of the title anion with tetrathiafulvalene (TTF) and bis(ethylenedithio)–TTF (BEDT–TTF).

The salt [Na(cis-anti-cis-dicyclohexyl-18-crown-6)][Ni(dmit) 2 ] 4 ·2Me 2 CO (dmit=1,3-dithiol-2-thione-4,5-dithiolate) has been prepared by electrocrystallisation and characterised by X-ray crystallography showing an unusual 1:4 cation:anion ratio. It consists of parallel stacks of [Ni(dmit) 2 ] 0.25– complexes separated by the Na + counter ion complexed by dicyclohexyl-18-crown-6 and two acetone molecules. The electrical conductivity, magnetic susceptibility and thermoelectric power of the salt have been measured and are consistent with semiconductor behaviour which is considered in conjunction with transfer integral calculations.

[Ethylpyridinium][Ni(mnt) 2 ] has been prepared by electrochemical oxidation of the corresponding dianionic salt. The X-ray structure has been determined. Three different environments were observed for the paramagnetic anions with two in a stacking mode and one approximately orthogonal to the stack. The stacking showed an ACA-type repeat unit with an inversion centre on complex C. Magnetic susceptibility measurements show Curie-Weiss behaviour with a change in parameters at around 50 K. Above this temperature a Curie constant of 0.3 emu K mol –1 and a Weiss constant of –150 K were observed and below 50 K these values were 0.08 emu K mol –1 and +2 K respectively. A maximum in the susceptibility was observed at 285 mK which suggests low temperature ordering to a phase with a non-cancelled alignment of the spins. Intermolecular interactions and the effect of temperature were assessed in terms of transfer integral calculations.

Three kinds of [Ni(dmit)2] (dmit = 2-thioxo-1,3-ditiol-4,5-dithiolate) salts containing 12-crown-4, 15-crown-5 or 18-crown-6 were prepared. In the crystal, the crown ethers form supramolecular assemblies in which counter cations are included. Lithium ions are located in the dimeric penta-coordinated ion cavity of [Li+]2[12-crown-4]3 unit of the [Li+]2[12-crown-4][Ni(dmit)2]7[acetone]2 crystal. Each Li+ cation is coordinated by four oxygen atoms of a 12-crown-4 molecule and the oxygen of a second 12-crown-4 molecule which form a bridge to a further Li+ cation. Two 15-crown-5 molecules sandwich a NH4+ cation in the salt of [NH4+][15-crown-5]2[Ni(dmit)2]. The NH4+ ion is deca-coordinated by oxygen atoms of 15-crown-5 through weak hydrogen bonding. The cation–crown ether unit forms a dimer resulting in a barrel-like supramolecular cation. The [NH4+][18-crown-6][Ni(dmit)2]3 complex is composed of segregated trimer stacks of Ni(dmit)2 and isolated ion-captured cavities of [NH4+][18-crown-6]. The NH4+ ion is fully included in the cavity, and is tightly bounded through strong hydrogen bonds to the oxygen atoms of 18-crown-6, resulting in a disk-shaped supramolecular cation. The salts of [Li+]2[12-crown-4]3[Ni(dmit)2]7[acetone]2 and [NH4+][18-crown-6][Ni(dmit)2]3 show semiconducting behaviour with the room-temperature conductivities of 30 and 0.4 S/cm, respectively, while [NH4+][15-crown-5]2[Ni(dmit)2] is insulating due to the mono-cation state of [Ni(dmit)2].

Reaction of [WI 2 (CO){Ph 2 P(CH 2 )PPh 2 }( η 2 -MeC 2 Ph)] mono(1-phenylpropyne) complex [WI 2 (CO){Ph 2 P(CH 2 )PPh 2 }( η 2 -MeC 2 Ph)] ( 1 ) in high yield. The structureof 1 has been determined by single crystal X-ray diffraction. The structure can best be described as a distorted octahedron with the two phosphorus atoms of the Ph 2 P(CH 2 )PPh 2 ligand trans to an iodo- and a 1-phenylpropyne ligand in the equatorial plane and the other iodo and carbonyl groups in the axial sites. The two bond lengths of the two W-I and those of the two W-P bonds are quite different reflecting the nature of the trans -ligands. Variable temperature 31 P NMR studies have been carried out on 1 , which has enabled the activation energy for alkyne rotation, to be calculated.

Reaction of [WI2(CO)3(NCMe)2] with 2 equivalents of thiophene-3-acetonitrile {NCCH2(3-C4H3S)} gave the crystallographically characterised complex [WI2(CO)3{NCCH2(3-C4H3S)}2] (1). The structure of 1 can be described as a distorted capped octahedron with a carbonyl group in the capping position, two carbonyl groups and an iodide in the capped face and two acetonitrile ligands and an iodide in the uncapped face. Treatment of the seven-coordinate complex [WI2(CO)3(NCMe)2] with an equimolar amount of L {L=AsPh3 (2) or PPh3 (3)} followed an in situ reaction with by one equivalent of thiophene-3-acetonitrile afforded the mixed ligand complexes [WI2(CO)3{NCCH2(3-C4H3S)}L] {2 (crystallographically characterised) and 3}. The structure of 2 also has a capped octahedral geometry, again having a carbonyl ligand in the unique capping position.

Lithiation of 4,5-bis(methylsulfanyl)-TTF 9, 4,5-(ethylenedisulfanyl)-TTF 10, 4,5-dimethyl-TTF 11 and 4,5,5′-trimethyl-TTF 12 (TTF=tetrathiafulvalene) followed by reaction with methyl isothiocyanate affords the corresponding (N-methylthio-carbamoyl)-TTF derivatives 14–17, respectively, in 54–70% yields. These new TTF derivatives display a broad intramolecular charge-transfer band in their UV–VIS spectra arising from conjugation between the donor TTF ring and the acceptor N-methylthiocarbamoyl moiety. Steric hindrance between the adjacent N-methylthiocarbamoyl and methyl substituents in 17 causes a marked hyposchromic shift in this band (λmax 395 nm) compared to compounds 14–16 (lambda;max 435–467 nm). Consistent with the electron-withdrawing properties of the N-methylthiocarbamoyl substituent, its attachment to the TTF ring raises slightly the oxidation potential of the system. Charge transfer complexes of these donors and (N-methylthiocarbamoyl)-TTF 2 with 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) and salts with bromide anions are reported, some of which have high room temperature conductivity values. The X-ray crystal structures are presented for 16, 17 and the salts 2·Br, 14·TCNQ and (17)2·20. The structure of 16 comprises orthogonal dimers (kappa packing) while in the structure of 17 individual molecules are orthogonal to each other. There is weak intermolecular hydrogen bonding in both 16 and 17. In the structure of 2·Br, the radical cations 2+· are almost planar and they form an infinite stair-like stack of dimers, with bromide anions situated between the stacks, and linked with the cation by a strong N–H‥Br bond. The structure of 14·TCNQ comprises mixed ‥DDAADD‥ stacks; the N-methylthiocarbamoyl group engages in an interstack N–H‥N bond with a TCNQ anion. Analysis of the bond lengths in the structure suggests that there is partial charge transfer from 14 to TCNQ. In the structure of (17)2·20 molecules form mixed ‥DDADDA‥ stacks and analysis of bond lengths suggests that there is only a small degree of charge transfer from donor to acceptor. The geometries of compounds 2, 14, 16, 17 were optimised using the PM3 semi-empirical method and the results compare favourably with the X-ray structural data.

Mono-tetrabutylammonium salts of nickel, copper, and gold 1,3,5-trithiepin-6,7-dithiolato (ttdt) complexes1a–c have been prepared and the structures of 1b and 1c determined by X-ray crystallography. Cyclic voltammograms of these complexes showed oxidation peaks in the range 0.23–0.46 V (vs. SCE). Partially oxidised salts of these complexes were obtained either as amorphous or polycrystalline solids. The electrical conduction properties are reported. The crystal structure of (TTF)[Au(ttdt)2 ] obtained from the reaction of 1c and TTF3(BF4)2 was determined by X-ray crystallography.

The complexes [P(C6H5)4][M(diod)2] [where MNi, Pd, Cu or Au (2a,b,c,d)] have been prepared and characterized spectroscopically, electrochemically and by X-ray structure determination for 2c. Preparation of 2d involved isolation of an intermediate complex with only one diod ligand. The Ni complex 2a forms semiconducting charge transfer complexes with TTF and BEDT-TTF.

Reaction of the complexes [WI 2 (CO) 3 L 2 ] [L 2 = (PEt 3 ) 2 , (PPh 3 ) 2 or Ph 2 P(CH 2 ) 2 PPh 2 = dppe] with 1 equivalent of Na 2 [S–S] (S–S = C 3 S 5 or maleonitriledithiolate) or H 2 bdt (benzene-1,2-dithiol) in acetonitrile and ethanol at room temperature afforded good yields of the six-co-ordinate compounds [W(S–S)(CO) 2 L 2 ] by displacement of the iodide ligands and a carbonyl ligand. X-Ray crystallographic studies were carried out on [W(S–S)(CO) 2 L 2 ] [S–S = C 3 S 5 , L 2 = (PEt 3 ) 2 ; S–S = bdt, L 2 = (PEt 3 ) 2 or L 2 = dppe]. The three structures are all six-co-ordinate with geometries intermediate between octahedral and trigonal prismatic but closer to the latter.

Metal complexes of 1,2 dithiolene ligands are known to exhibit unusual solid state properties. The properties of the Mercury complexes of the new type of 1,2 dithiolene ligand which includes the TTF molecule framework is described. The structure and magnetic properties of the ferromagnet NH4[Ni(mnt)2].H2O are discussed.

The new TTF-based organic donor BMTP-TTF has been synthesised by a phosphite mediated coupling of two thione units and characterised by x-ray crystallography. This reaction involved abstraction of a sulphur atom from the seven membered ring of the thione to give a six membered ring at each end of the symmetrical product.

[Ni(dpdt) 2 ] (H 2 dpdt = 6-methylene-1,4-dithiepin-2,3-dithiol) has been prepared from [NBu 4 ][Ni(dpdt) 2 ], using both chemical and electrochemical methods. Electrical conduction studies indicate that the compound is a semiconductor (σ RT = 10 −5 S cm −1 ). The X-ray crystal structure of [Ni(dpdt) 2 ] is reported.

The synthesis and physical properties of a series of soluble, tetrakis(n-alkylthio)nickel bis(ethylene-1,2-dithiolene), [TTCn-Ni(edt)2] complexes (n= 4–11) is described. The room-temperature electrical conductivities of these materials in the undoped state are reported and the X-ray crystal structures of the n= 4 and 6 derivatives have been determined.

High-pressure resistivity studies on s-[CH 3 ) 4 N][Pd(dmit) 2 ] 2 and [(CH 3 C 2 H 5 ) 2 N]-[Pd(dmit) 2 ] 2 have revealed the system to be new molecular superconductors with T c =6.3 K at 6.5 kbar and T c =4K at 2.4kbar, respectively. s-[(CH 3 ) 4 ][Pd(dmit) 2 ] 2 , though they have the isomorphous to the high-pressure superconductor, [(CH 3 ) 4 N][Ni(dmit) 2 ] 2 has the structure almost dimeric columns of Pd(dmit) 2 molecules. The determination of the phase diagram has revealed the existence of a narrow temperature region where the superconducting phase invades into the insulating phase. The crystal of [(CH 3 ) 2 (C 2 H 5 ) 2 N][Pd(dmit) 2 ] 2 belongs to triclinic system and has the dimeric columns of Pd(dmit) 2 . It is of interest that the insulating phase emerges when superconducting state is suppressed at high pressure.

We report on the magnetic and transport properties of the organic salt NH 4 Ni(mnt) 2 H 2 O where (mnt) is the maleonitrile dithiolate ligand. This material is antiferromagnetic down to 100K, below which there is a transition to a paramagnetic state with ferromagnetic exchange. This is accompanied by an increase in resistivity by a factor of two which we consider indicative of a structural phase transition. Long range ferromagnetic order is seen below 4.9K.

BTDA-TFF has beensynthesised from 2,5-(thiadiazole)-3,4-trithiocarbonate via triethylphosphate coupling. The X-ray structure and properties of this new donor are reported.

The preparation, structure and electrical conductivity of metal complexes of mnt and dmit with Group 1 cations are described.

Polarized reflectance spectra of single crystals of (CH 3 ) 4 As[Pd(dmit) 2 ] 2 and Cs[Pd(dmit) 2 ] 2 were measured and compared with those of (CH 3 ) 4 N[Ni(dmit) 2 ] 2 . Prominent absorption bands, which do not exist in the reflectance spectra of (CH 3 ) 4 N[Ni(dmit) 2 ] 2 were observed around 10000cm −1 in the spectra of [Pd(dmit) 2 ] salts. Analysis of the reflectance spectra reveals the anomalous electronic structure in these salts where the energy levels derived from HOMO and LUMO of one molecule are partly inverted due to their strongly dimerized structure.

The reaction of [WI2(CO)3(NCMe)2] with two equivalents of PEt3 in Et2O/CH2Cl2 gives the MeCN-displaced product [WI2(CO)3(PEt3)2] (1) in high yield. The crystallographically determined solid state structure of (1) shows the complex to be capped octahedral with a carbonyl ligand capping an octahedral face containing the two octahedral carbonyls and one PEt3 group. The other face contains the two iodo ligands trans to carbonyl groups, and the second PEt3 ligand trans to the first PEt3 group. The low temperature (-30°C) 13C-{1H}-n.m.r. spectrum of (1) correlates with the solid state structure, and the fluxional properties of (1) have been investigated by VT 31P-{1H}-n.m.r.spectroscopy.

The title radical ion salts of 4-iodotetrathiafulvalene1 have been prepared and their X-ray crystal structures determined at 150 K. The 2:1 salt [ITTF .+ ] 2 {Pd[S 2 C 2 (CN) 2 ] 2 } 2- 3forms a mixed stack structure in which the Pd(mnt) 2 anions intermingle with pairs of iodo-TTF radical cations, i.e. a DDADDA stacking arrangement. The structure of the 1:1 salt ITTF .+ HSO 4 - 4 comprises stepped stacks of ITTF cations with two alternating modes of overlap. Between the cation stacks there are infinite chains of hydrogensulfate anions, linked by hydrogen bonds. Both structures are characterised by short intermolecular contacts involving the iodine substituent.

The [(M+)x[18]crown-6)] supramolecular cations (SC+), in which M+ and [18]crown-6 are alkali metal ions (M+ = Li+, Na+, and Cs+) and 1,4,7,10,13,16-hexaoxacyclooctadecane, respectively, form ionic channel structures through the regular stacks of [18]crown-6 in [Ni(dmit)2]-based molecular conductors (dmit2+ = 2-thioxo-1,3-dithiole-4,5-dithiolate). In addition to the [Ni(dmit)2] salts that have the ionic channel structures (these salts are abbreviated as type I salts), Li+ and Na+ form dimerized [(M+)2([18]crown-6)2] units in the crystals (type II salts). The K+ and Rb+ are coordinated tightly into the [18]crown-6 cavity to form typical disk-shape SC+ units in the corresponding [Ni(dmit)2] salts (type III salts). The type I, II, and III salts have typical stoichiometries of [(M+)x([18]crown-6)][Ni(dmit)2]2, [(M+)([18]crown-6)(H2O)x(CH3CN)(1.5 - x)][Ni(dmit)2]3 (x = 1 for Li+ or 0.5 for Na+), and [M+([18]crown-6)][Ni(dmit)2]3, respectively: the salts of the same type are isostructural. In agreement with the trimer structures of [Ni(dmit)2] in the type II and III salts, they exhibit semiconducting behavior with electrical conductivities at 300 K (sigma(300 K)) of 0.01-0.1 S cm(-1). Type I salts contain a regular stack of partially oxidized [Ni(dmit)2] units, which form a quasi one-dimensional metallic band within the tight-binding approximation regime. The electrical conductivities at 300 K are 10-30 S cm(-1), and an almost temperature-independent conductivity was observed at higher temperatures. However, the one-dimensional electronic structures in these salts are strongly influenced by the static and dynamic structures of the coexisting ionic channel. The Na+ salt is a semiconductor, whose magnetic behavior is described by the disordered one-dimensional antiferromagnetic chain. On the other hand, the Cs+ salt is a exhibits metallic properties with 2 kF instability at room temperature. The Li+ salt shows a gradual transition from the high-temperature metallic phase to the low-temperature one-dimensional antiferromagnetic semiconductor phase, which was associated with the freezing of Li+ motion at lower temperatures. The preferential crystallization of type I salts was possible by controlling the equilibrium constant (Kc) of the complex formation between M+ ions and the [18]crown-6 molecule. The ionic channel structures were obtained when the KC was low in the electrocrystallization solution, while type II or III salts were formed in the high Kc region.

Monovalent cations (M+ = Na+, K+, Rb+, and NH4+) and 12-crown-4 were assembled to new supramolecular cation (SC+) structures of the M+(12-crown-4)n (n = 1 and 2), which were incorporated into the electrically conducting Ni(dmit)2 salts (dmit = 2-thioxo-1,3-dithiole-4,5-dithiolate). The Na+, K+, and Rb+ salts are isostructural with a stoichiometry of the M+(12-crown-4)2[Ni(dmit)2]4, while the NH4+ salt has a stoichiometry of NH4+(12-crown-4)[Ni(dmit)2]3(CH3CN)2. The electrical conductivities of the Na+, K+, Rb+, and NH4+ salts at room temperature are 7.87, 4.46, 0.78, and 0.14 S cm-1, respectively, with a semiconducting temperature dependence. The SC+ structures of the Na+, K+, and Rb+ salts have an ion-capturing sandwich-type cavity of M+(12-crown-4)2, in which the M+ ion is coordinated by eight oxygen atoms of the two 12-crown-4 molecules. On the other hand, the NH4+ ion is coordinated by four oxygen atoms of the 12-crown-4 molecule. Judging from the M(+)-O distances, thermal parameters of oxygen atoms, and vibration spectra, the thermal fluctuation of the Na+(12-crown-4)2 structure is larger than those of K+(12-crown-4)2 and Rb+(12-crown-4)2. The SC+ unit with the larger alkali metal cation gave a stress to the Ni(dmit)2 column, and the SC+ structure changed the pi-pi overlap mode and electrically conducting behavior.

Single crystals of [FcCH(2)N(CH3)(2)][Ni(C5S)(2)] have been grown in a typical H-type cell charged with [FcCH(2)N(CH3)(3)](I) and [(n-C4H9)(4)N](2)[Ni(C-3 S-5)(2)]. It belongs to the monoclinic system, P2(1)/n, a = 6.383(2), b = 18.810(7), c = 16.575(4) Angstrom, beta = 96.32(2)degrees, V = 1977.8(11) Angstrom (3) and Z = 4. Electrical conductivity measurements have shown that it is an insulator with a room temperature conductivity of 10(-7) S/cm. The low value for the conductivity is due to the absence of anion stacks and short S...S contacts in the crystal structure. Neutral complex [Ni(C3S5)(2)] was prepared by the diffusion process between [(n-C4H9)(4)N](2)[Ni(C3S5)(2)] and [FcCH(2)NH(CH3)(3)](BF4) in CH3CN. It showed a room temperature conductivity of 2 x 10(-2) S/cm.

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 [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.

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.

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.

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 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.