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The synthesis and electropolymerisation of a new terthiophene, 1,3-di-2-thienylthieno[3′,4′:5,6][1,4]dithiino[2,3-b]quinoxaline, is reported. The compound bears a quinoxaline unit fused to the central thiophene ring via a 1,4-dithiin ring; the latter unit ensures a non-planar structure for the molecule. The corresponding polymer, prepared electrochemically, has been characterized by cyclic voltammetry and UV-vis-NIR spectroelectrochemistry. The material is oxidised within the conjugated chain, but the reduction processes are complex and arise from both the polythiophene and the independent quinoxaline units. The polymer has two distinct colour states—orange in the neutral form and green–blue in the oxidised state. Electrochromic studies on poly(1,3-di-2-thienylthieno[3′,4′:5,6][1,4]dithiino[2,3-b]quinoxaline) reveal fast switching speeds that are superior to those of poly(3,4-ethylenedioxythiophene) (PEDOT) and a colouration efficiency of 381 cm2 C−1 at 650 nm.

The synthesis of five new dihalogen/interhalogen charge transfer adducts featuring cyano and nitro functionalized 1,3-dithiole-2-thiones have been prepared and characterized by x-ray crystallography. The structures feature a complex series of intermolecular close contacts between heteroatoms, as well as hydrogen bonding, to give highly ordered, polymeric assemblies. The adduct 4.IBr crystallizes in a noncentrosymmetric chiral space group and features a stack of molecules assembled through hydrogen bonds. The functional groups of all adducts participate in networks of close contacts, but do not affect the coordination environment of the dihalogen/interhalogen species.

A new series of oligothiophenes bearing electron deficient fluorene units have been prepared and characterised. The materials are functionalised by C8/C11 alkyl chains or triethylene glycol side groups, yet the higher oligomers remain poorly soluble. The absorption characteristics of a sexithiophene analogue (compound 3) have been studied by UV-vis and photoinduced absorption spectroscopy. Photovoltaic cells have been fabricated from blends of 3 and fullerene derivative [6,6]-phenyl-C61 butyric acid methyl ester (PCBM). The photocurrent spectrum of the device matches the absorption spectrum of the sexithiophene system which incorporates an intramolecular charge transfer band arising from the 1,3-dithiole-fluorene units. A modest power conversion efficiency of 0.1% was achieved.

New halogen adducts of 1,3-dithiole-2-thione-4-carboxylic acid and dimethyl 1,3-dithiole-2-thione-4,5-dicarboxylate have been prepared and characterised by X-ray crystallographic studies. The adducts feature an array of intramolecular and intermolecular close contacts involving chalcogen-chalcogen, chalcogen-halogen and halogen-halogen interactions. Whilst these contacts are derived from the basic heterocyclic unit and the coordinated halogen molecules, the ester and acid functionalities provide a varied and rich array of hydrogen bonding motifs, which significantly enhance the long-range order of the supramolecular structures.

We report the synthesis and electropolymerisation of 1,3,5-tris(1,3-dithiole-2-ylidenephenylene)benzene 4. The resulting polymer features extended tetrathiafulvalene (TTF) units and can be considered as a cross-conjugated, cross-linked structure. Upon p-doping, electrochemical and UV-vis spectroelectrochemical experiments indicate that the polymer undergoes a unique coformational change within the dendralene unit from one definitive orthogonal arrangement to another.

This paper describes the strategy toward novel monodisperse, well-defined, star-shaped oligofluorenes with a central truxene core and from monofluorene to quaterfluorene arms. Introduction of solubilizing n-hexyl groups at both fluorene and truxene moieties results in highly soluble, intrinsically two-dimensional nanosized macromolecules T1-T4. The radius for the largest oligomer of ca. 3.9 nm represents one of the largest known star-shaped conjugated systems. Cyclic voltammetry experiments reveal reversible or quasi-reversible oxidation and reduction processes (Eox = +0.74 to 0.80 V, Ered = -2.66 to 2.80 eV vs Fc/Fc+), demonstrating excellent electrochemical stability toward both p- and n-doping, while the band gaps of the oligomers are quite high (EgCV = 3.20-3.40 eV). Close band gaps of 3.05-3.29 eV have been estimated from the electron absorption spectra. These star-shaped macromolecules demonstrate good thermal stability (up to 400-420 degrees C) and improved glass transition temperatures with an increase in length of the oligofluorene arms (from Tg = 63 degrees C for T1 to 116 degrees C for T4) and show very efficient blue photoluminescence (lambdaPL = 398-422 nm) in both solution (PhiPL = 70-86%) and solid state (PhiPL = 43-60%). Spectroelectrochemical experiments reveal that compounds T1-T4 are stable electrochromic systems which change their color reversibly from colorless in the neutral state (approximately 340-400 nm) to colored (from red to purple color; approximately 500-600 nm) in the oxidized state.

A new family of tetrathiafulvalenes has been prepared. The materials exhibit complex redox behaviour related to the electronic influence of the 1,4-dithiin moieties embedded within the framework of the molecules. The X-ray crystal structure of compound 4 reveals an unusual non-planar conformation of the heterocyclic compound, with the TTF fragment adopting a boat conformation. Theoretical calculations, performed at the DFT level (B3P86/6-31G*), confirm the boatlike structure (C2v symmetry) as the most stable conformation for this family of tetrathiafulvalenes. Upon oxidation, electrons are extracted from the whole molecule and the radical cations and dications remain highly distorted from planarity. For the dications, the 1,4-dithiin units present foldings of ∼40° suggesting the possibility of reaching higher oxidation states in agreement with experimental results. For the tetracations, both the TTF nucleus and the 1,4-dithiin units are singly-charged and become planar. The tetracations therefore present fully-planar, π-delocalised structures and are stabilised by the gain of aromaticity of the TTF and 1,4-dithiin electron-donor units.

The polymerisation of a fused 2,5-dibromothieno-TTF derivative has been achieved using Ni(COD)(2) as the catalyst. Whilst higher molecular weight fractions are sparingly soluble, lower weight samples are soluble in common organic solvents. Cyclic voltammetry shows that the polymer undergoes two reversible oxidation processes at +0.71 and +1.10 V (vs. Ag/AgCl), respectively. The optical and electrochemical band gaps have been deduced by electronic absorption spectroscopy and cyclic voltammetry and are in the range 1.75-1.89 eV. Independent conductivity measurements by impedance spectroscopy and four-probe methods give values of 5 x 10(-7) and 7 x 10(-6) S cm(-1) for the neutral polymer. The highest conductivity for the doped material as a thin film (0.1 S cm(-1)) was obtained from a drop cast solution of poly(11)/TCNQ (1 : 2 molar ratio). EPR and UV-vis spectroelectrochemical experiments reveal that both oxidation processes are centred on the TTF unit of the polymer. Chronocoulometric experiments show that almost two electrons per repeat unit are released upon oxidation at +1.3 V.

This paper describes the chemical and electrochemical synthesis of novel copolymers of thiophene and pyridine. Di-iodination of 3-hydroxypyridine 12 followed by O-substitution gave a series of ethers 14b–d and esters/carbamates 15a–d which were reacted with the stannylated bithiophene derivative 17 in a Stille cross-coupling reaction yielding poly (1b–d) and poly (2a–d) respectively. These chemical polymerisation reactions generally resulted in highly insoluble materials which were difficult to characterise. Ethers 14b–d and esters/carbamates 15a–d gave O-substituted 3-hydroxy-2,6-di(2-thienyl)pyridines 1b–d and 2a–d respectively in Stille cross-coupling reactions with the stannylated thiophene 16. Ethers 1b–d underwent electrochemical polymerisation allowing the synthesis of O-alkylated polymers, poly (1b–d), with electrochemical band-gaps of 1.4 to 1.6 eV. In contrast, the esters/carbamates 2a–d could not be electropolymerised.

The synthesis of a new series of sulfur-rich ligands is reported. These compounds, which are related to the dmit(2-) (2-thioxo-1,3-dithiol-4,5-dithiolato) structure, comprise two 2-thioxo-1,3-dithiol-5-thiolato units linked by a bridging unit at the 4-position of the heterocycle via a dithioether spacer unit. Complexation reactions have been carried out on a variety of metal centres; dialkyl tin and gold(I) derivatives have been isolated and fully characterised. The X-ray crystal structure of an octahedral Ni(II) complex, involving two coordinating pyridine molecules, is presented.

The syntheses and electrochemistry of thieno[3',4'r5,6][1,4]dithiino[2,3-b]quinoxaline (9), 2,3-bis(methylsulfanyl)[1,4]dithiino[2,3-b]quinoxaline (16) and 2,3-ethylenedisulfanyl[1,4]dithiino[2,3-b]quinoxaline (17) are reported, together with the X-ray crystal structures of 9, 16 and the charge-transfer complex 9.TCNQ. In the thieno derivative 9, the molecular structure undergoes a significant change from a boat conformer to a planar system, upon oxidation with TCNQ. Theoretical calculations show that oxidation leads to planarisation of the molecular structure due to the aromatisation of the dithiine moiety. The study of the oxidised/reduced species helps to rationalise the electrochemical behaviour observed experimentally.

The novel annelated monomer thieno[3′,4′:5,6][1,4]dithiino[2,3-b]quinoxaline 1 has been electropolymerised on a variety of electrodes, resulting in films which are electroactive in non-aqueous and aqueous solution. The polymer films exhibit a transformation in voltammetric response corresponding to a positive shift in redox potential in the presence of silver cation, the maximum shift being ca. 150 mV in acetonitrile and ca. 400 mV in aqueous LiClO4 solution. Mercury dication demonstrates a similar, but smaller (ca. 130 mV) shift in aqueous solution. Theoretical calculations clearly show the potential of poly(1) as a metal complexation agent. The Ag+ ion coordinates with 1 in two ways: (i) an apical conformation involving the two dithiine sulfurs and (ii) a lateral σ-complex with a contribution from the quinoxaline nitrogens. The Hg2+ ion prefers to coordinate with the sulfur atoms. The calculations performed for the trimer illustrate that the metal ions can be coordinated simultaneously by two repeat units in the polymer chain.

The high-temperature heat-exchanging oil Lutron KS1, a poly(ethylene glycol) containing a single benzene ring in the chain with 1,3-substitution, has been characterised by 1 H and 13 C NMR spectroscopy, IR, matrix-assisted laser desorption ionisation time-of-flight (MALDI-TOF) mass spectrometry and size exclusion chromatography (SEC); the latter shows it to have a low PDI (1.06) while 1 H NMR and MALDI-TOF indicate a peak molecular mass of 816 and 682 respectively. The 20-fold rise in viscosity of Lutron during industrial use at 170–210°C over prolonged periods is shown to be due to the effect of oxygen in causing degradation to give carbonisation and the release of a range of volatile degradation products including CH 3 CHO, H 2 O, and di- and tri(ethylene glycols). Thermal degradation under N 2 gives a much more complex array of volatiles, including 18-crown-6; the formation of most of these involves simple homolysis followed by disproportionation. The SEC chromatograms of residual Lutron were bimodal, indicating extensive formation of high mass products. The 1% addition of various well-known antioxidants had only, at best, a marginal effect on reducing the oxygen-induced degradation; the most effective method of extending the service life of Lutron is to exclude oxygen during the heating process.

The chemical synthesis of a novel polyfuran, poly(2,3-bis(hexylthio)-[1,4] dithiino[2,3-c]furan) (PBDF), substituted at the 2,3-positions with an S-alkylated dithiin unit, is reported. The new polymer has been characterized in terms of its electronic absorption, electrochemical, and thermal properties. Employment of the dithiin moiety provides intrinsic additional electroactivity, as well as a functional handle for substitution with alkyl groups, enhancing the processability of the polymer. The new polymer is compared with the closely related and well-established literature compounds PEDOT and PEDTT as well-studied, highly chalcogenated polythiophenes. Polyfuran with sulfur substituents in the backbone, in the form of a fused dithiin ring is prepared and characterized. The polymer can be regarded as an inverse analog of PEDOT, featuring sulfur-oxygen noncovalent contacts between repeat units that help to planarize and rigidify the polymer backbone.

An analysis is performed on the molecular and electronic features in a series of trigonal molecules constituted by a central truxene core which is ramified with three oligofluorene moieties of different lengths. Arms and core are studied independently and upon threefold unification. Special emphasis is paid to the modulation of the conjugational properties in relation to substitution, molecular dimension, ring aromaticity, intermolecular forces, oxidation state, etc. Raman and optical absorption/emission spectroscopies in conjunction with computational theoretical results are combined for this purpose. The evolution of some key intensity ratios in the Raman spectra (i.e., I(1300)/I(1235)) is followed as an indication of electronic interaction between the core and the branches. The changes of the electronic delocalization upon solvation, with varying temperature in the solid state, with the nature of the aromatic unit (bithiophene/fluorene) or after electrochemical oxidation are interpreted. The modulation of the optical properties on the basis of the structure and energetics of the orbital around the gap is also addressed. Density functional theory was used to assign the vibrational and electronic spectra.

[structure: see text] We report the synthesis of a novel end-capped sexithiophene derivative bearing two pendent, fused tetrathiafulvalene (TTF) units linked to the main chain through 1,4-dithiin heterocycles. Cyclic voltammetry and absorption spectroscopy are used to investigate the electronic properties of this hybrid electroactive material. The oligomer has a band gap of 2.1 eV, and the material can be oxidized through the sexithiophene and TTF units simultaneously.

The reaction of 4-ferrocenyl-1,3-dithiole-2-thione with diiodine affords an unprecedented "double" charge-transfer complex; the highly ordered ferrocenium units are held by a supramolecular polyiodide chain, and the material shows evidence of the formation of zigzag magnetic chains below 2 K.

Bis(dithiolene) metal complexes incorporating fused terthiophene units have been prepared; the nickel analogue undergoes electropolymerisation to afford a low bandgap material with very broad absorption characteristics.

The synthesis of a novel series of transition metal ligands and complexes is reported; the materials are related to the well-studied DMIT systems, allowing greater versatility in terms of structural design and processability.

The crystal structure of an iodine monobromide adduct of dimethyl 1,3-dithiole-2-thione-4,5-dicarboxylate reveals a layered polymeric network of donor and acceptor molecules linked primarily through S⋯I–Br charge-transfer and hydrogen bonded interactions.

Luminescent lanthanide complexes have been prepared by exploiting the interaction between lanthanide DO3A complexes and chromophore bearing carboxylates or phosphonates. This interaction can be utilised to probe the choice of sensitising chromophore suited to a given lanthanide. Furthermore, ternary complexes obtained from chromophore appended carboxylates dissociate in the presence of phosphate, while those obtained from phosphonates do not.

The title compound has been reacted with I2, IBr and ICl to afford the charge-transfer adducts 4·2I2, 4·IBr and 4·ICl·½I2, respectively. The products have been characterised by Raman and IR spectroscopy and X-ray crystallography. The adducts contain linear S⋯I–X (X = I, Br or Cl) units (174–178°) in which the S⋯I contacts range from 2.534–2.597 A. In 4·2I2 and 4·ICl·½I2, the materials contain additional ‘free’ diiodine units which are held within a matrix of intermolecular contacts, predominantly through non-covalent halogen–halogen and sulfur–halogen interactions. Although the functional groups in the parent molecule (4) are inert at the supramolecular level, the bromomethyl groups in the adducts contribute strong interactions through Br⋯Br, Br⋯I, Br⋯S and Br⋯H close contacts. The structures of the complexes are polymeric in nature, providing interactions in two and three dimensions.

Three new, highly crystalline 2,5-dibromothiophene compounds polymerise on standing in the absence of solvent and catalyst; X-ray crystallography shows that the molecules are held in close proximity by several short intermolecular contacts, facilitating the coupling of monomers.