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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).

A monodithiolate gold complex ( 1 ), potassium[dichloro(1,3,5-trithiepin-6,7-dithiolato)aurate] was isolated in a 1:1 reaction of 1,3,5-trithiepin-6,7-dithiolato (ttdt) and potassium tetrachloroaurate. 1 was characterised by its elemental analysis, IR and Raman spectra.

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.

Metallic behaviour is well known in charge-transfer complexes that contain stacks of planar, partially oxidized (or reduced) π-conjugated molecules. Electronic conduction occurs in the partially occupied, delocalized π bands formed by intermolecular orbital overlap, and some of these materials exhibit superconductivity1,2. Counter-ions, present to achieve charge neutrality, usually play a passive role, although in some cases they couple to the electronic structure, for example by imposing a new structural periodicity (a superlattice) by orientational ordering1. The development of molecular solids that can simultaneously support the transport of both electrons and ions is important for several fields, including the development of solid-state batteries3,4, electroluminescent devices5 and biomimetic systems6,7. Crown ethers are promising components for such systems, as they provide cavities through which ion motion might occur. Here we report that the charge-transfer salt Li0.6(15-crown-5-ether)[Ni(dmit)2]2·H2O exhibits both electron and ion conductivity: the stacks of the nickel complex (dmit is an organic molecule) provide a pathway for electron conduction, and stacks of the crown ethers provide channels for lithium-ion motion. Evidence for the latter above 250 K is provided by NMR and conductivity studies. We also see evidence for coupling of the electron and ion motions. This compound might serve as a model for the development of other hybrid electronic/ionic conducting materials.

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.

The synthesis and solution electrochemical properties of two novel 3-thienyl substituted tetrathiafulvalene (TTF) donors 7 and 11 are described. The single-crystal X-ray structure of 7 is reported, which is characterized by the presence of short intermolecular SS contacts. Cyclic voltammetry of the derivatives indicates that two reversible redox waves, characteristic of TTF derivatives, are present. Attempts were made to electropolymerize the two derivatives at a platinum electrode in dichloromethane. Formation of a blue-coloured solid, characteristic of the thiophene radical cation species, was observed for one of the derivatives, but it was not possible to isolate a polymer on the working electrode. Preliminary electropolymerization studies on the TTF ‘half unit’ 6 are also reported.

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.

The behaviour of floating layers ofN-octadecylpyridinium–Pd(dmit)2 , complex 1, on the surface of a pure water subphase has been studied using pressure versus area isotherm measurements. Film properties were dependent on the quantity of material spread and the length of time that the layer was aged on the surface of the subphase before compression (spreading time). Area per complex values suggested that a monolayer was formed only if a small amount of material was applied to the subphase and the spreading time was long (several hours). Multilayer Langmuir–Blodgett (LB) films have been deposited onto hydrophilic glass substrates and examined using surface profiling, scanning electron microscopy with energy dispersive X-ray spectroscopy and optical absorption spectroscopy. Observations using electron microscopy showed that films deposited from fresh floating layers contained aggregates that were tens of microns in size. In contrast to previous studies on multilayer films of N-octadecylpyridinium–Ni(dmit)2 complex, the LB films of complex 1 were electrically conductive without any post deposition doping treatment, with room temperature, in-plane conductivity values as high as 0.15±0.10 S cm–1 . In some cases, super-Ohmic current versus voltage characteristics were recorded, which has been attributed to space-charge-limited conductivity. Multilayers transferred from aged floating layers did not exhibit significant bulk conductivity, either in the as-deposited state or after iodine doping, although some samples contained highly conductive crystallites that were several hundred microns in size. The single crystal X-ray structure of the analogous N-dodecylpyridinium–Pd(dmit)2 complex is reported, which provides the first structural study of a [Pd(dmit)2 ]–monoanion. The anions pack in centrosymmetric dimers, with an interplanar spacing of ca. 3.5 A and Pd‥S(5′) contacts of 3.57 A, which are separated by N-dodecylpyridinium cations (with a Pd‥N contact of 3.83 A).

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.

The facile synthesis of 4 and (±)- 6 was carried out via a Diels-Alder type [2+4] cycloaddition reaction of oligomeric dien 8 with styrene or t -stilbene, respectively, as a dienophile by a thermal reaction and/or photoreaction. (±)- 6 crystallized as a racemic compound composed of ( 2R,3R ) and ( 2S,3S ) enantiomers.

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 electronic contributions to the dipole moment, the polarizabilities, first and second hyperpolarizabilities for LiH are computed using basis sets for H involving two variations of a set comprising 10s 7p 5d GTOs, while for Li several large basis sets (e.g. (13s 8p 6d 2f)/[8s 5p 3d 1f] and 13s 7p 3d 1f) have been employed. Electron correlation has been taken into account using MP4[SDTQ] theory. The effect of the nuclear motion on the dipole moment and some components of the polarizability and hyperpolarizabilities is computed at the SCF level employing a finite perturbation theory approach. The vibrational contribution to the above properties is calculated for the ground and the first four excited vibrational states. We have found that vibrational contributions are not negligible and one (βzzz) has a significant magnitude.

Dianionic and neutral bis TTF dithiolate mercury and nickel complexes have been prepared. X-ray structural studies show the geometry around the mercury to be tetrahedral and CV and esr measurements indicate very little interaction between the two TTF based ligands. Conductivity measurements on the neutral mercury complexes gave [sgrave]RT = 10−5 Scm−1 whereas for the neutral nickel complexes values of 10−2 -10−1 Scm−1 are observed. The salts [TTF]x[Fe(tdas)2] × = 2, 3/2 (Idas = 1,2,5-thiadiazole-3,4-dithiol) have been prepared by electrocrystallisation and show conductivities of 10−2 Scm−1 and 10−5 Scm−1 respectively. The former salt displays thermally activated magnetic behaviour and the latter shows a Curie-type temperature dependance.

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.

Recent developments in the synthesis of metal complexes of sulphur-donor ligands are discussed, together with an account of the preparation of the new 1,2-dithiolate ligand 6-methylene-1,4-dithiepin-2,3-dithiol (H 2 dpdt). The structure and electrochemical properties of [Bu 4 N][Cu(dpdt) 2 ] are described.

[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.

A series of novel metallophthalocyanines (OC12H25)8MPc, where M = Zn, Cu, Ni and Co have been prepared. These compounds are based upon the known metal-free (2,3,9.10,16,17,23,24) octakis(dodecyloxy...

NH4Ni(mnt)2. H2O shows localized moments with antiferromagnetic coupling at room temperature. The antiferromagnetism persists down to 100K at which point there is an abrupt change in the slope of the susceptibility corresponding to an anomaly observed in the resistivity. Below 100K there is evidence for ferromagnetic coupling between the spins. The crystal has an orthorhombic space group Pnam, with a=12.096A, b=3. 918A, c=29. 216A, U=1384. 8A3 and Z = 4, and the crystal structure is highly anisotropic, in common with other charge transfer salts of this type. The anions form uniform stacks along the b-axis in which the molecules are tilted by 26° to the stacking axis. Results are presented here on the electrical and magnetic behaviour of this salt.

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.

New metal bis-diothiolene complexes have been prepared of the type M(dmad) 2 (M = Ni, Pd, Au). An investigation of their solution and solid state properties is reported.

The new multi-sulphur donor ligand ortho-xylenedithiodithiolate (OXDT-DT) has been prepared. Monoanionic complexes of OXDT-DT with Ni(ii), Cu(ii) and Au(iii) have been isolated as the (C4H9)4N salts. The monoanions are readily oxidised to the neutral metal complex by treatment with iodine or by electrochemical oxidation.

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 synthesis and electrochemical properties of several maleimide derivatives of 3-(2-aminoethyl)thiophene are described. Of the four soluble thiophene derivatives prepared only one, N -{3-(2-ethyl)thiophene}-3,4-dichloromaleimide, was capable of being polymerized electrochemically. The resulting polymer exhibited a conductivity of −5 S cm −1 . The influence that bulky maleimide groups have on preparing maleimide-substituted polythiophenes is discussed.

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

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 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.

The preparation of a poly(maleimide-ether) containing pendent thiophene rings via the reaction of 2-(3-thienylmethyl)-1,3-N,N'-bis(3,4-dichloromaleimido) propane with 1,4-dihydroxybenzene is described. The novel 2-substituted-1,3-N,N'-bis(3,4-dichloromaleimido) propanes were obtained by allowing their corresponding diamine hydrochlorides to react with 3,4-dichloromaleic anhydride in acetic acid in the presence of sodium methoxide. The diamine hydrochlorides were prepared by the reduction of their respective diamides. The poly(maleimide-ether)s were fully characterized and 13C-NMR spectroscopy was used to confirm the microstructure of the materials. The properties of the thiophene substituted polymer are compared with model poly(maleimide-ether)s. Electrochemical studies indicated that the thiophene rings in the thiophene-substituted poly(maleimide-ether) were not electroactive. © 1992 John Wiley & Sons, Inc.

The third order optical nonlinearity, χ (3) , of two polymers consisting of nickel dithiolene guest molecules in a polymethylmethacrylate host have been measured. The optical nonlinearly was measured by degenerated four wave mixing experiments at a wavelength of 1.06 μm using 100 ps laser pulses. χ (3) coefficients of up to 10 -17 m 2 /V 2 were observed corresponding to nonlinear refractive index, n 2 , of up to 10 -8 cm 2 /KW with a damaged threshold >1GW/cm 2

The p -acetoxybenzylthio protecting group has been found to be compatible with the triethylphosphite mediated cross-coupling of 4,5-dialkylthio-1,3-dithiol-2-ones, providing access to the tetrathiolate 5 , and to dithiolates 11a and 11b , which are excellent precursors for unsymmetrical tetrahioalkyl tetrathiafulvalene derivatives.

Metal complexes of sulphur-donor ligands have been widely studied, often because of their intense colours and redox properties.1 More recently they have been shown to exhibit a wide range of structures and properties in the solid state dependent upon the nature and extent of the interactions between the metal complex anions. The metallic and non-linear optical properties of these complexes have recently attracted special attention.2, 3

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

Low dimensional metals, in which the conduction electrons are confined to stacks or within layers, provide an important area of research into interactions in the electron gas and its coupling to the lattice. The metallic state is commonly unstable at low temperatures, and can be replaced by a wide variety of ground states, including the charge density wave (CDW) state, spin density wave (SDW) state, superconductivity etc. High pressure has always been an important experimental tool in this field, as many of the materials studied have high compressibilities, and it is often possible to switch from one ground state to another under pressure. We consider here the properties under pressure of a series of organo-metallic charge transfer salts in which the metallic behaviour is due to intermolecular delocalisation of the π electron systems of the ligand groups around the transition metal atom.

Condensation of 2-thioxo-1,3-dithiole-4,5-dithiolate dianion 2 with 1,5-dibromo-3-thiapentane gave largely the 2:2 macrocycle 4 which could be converted into the novel tetrathiafulvalene-cage macrocycle 5 on treatment with triethyl phosphite. Treatment of the dithiolate dianion 2 with 1,9-dibromo-3,7-dithianonane gave the 1 :1 macrocycle 6 which could be converted into the planar tetrathiafulvalene derivative 7. The cyclic voltammogram of 7 showed a marked response on the addition of silver perchlorate, but no response when alkali metal perchlorates were added. Crystal structures of macrocycles 3 and 5 are also reported.