Adam Charlton

Nickel dithiolenes containing pendant thiophene units: precursors to dithiolene-polythiophene hybrid materials{

The synthesis, electrochemical and spectroscopic properties of the new thiophene-substituted metal dithiolene complexes [Ni(b-3ted)2] (3) and [NBu4][Ni(b-3ted)2] ([NBu4][3]) are described [b-3ted = bis(3-thienyl)-1,2-ethylenedithiolene] and compared with new studies of the known compounds [Ni(b-2ted)2] (2) and [NBu4][Ni(b-2ted)2] ([NBu4][2]). X-Ray structures were determined for the neutral complexes 2 and 3 and both showed planar nickel dithiolene units with thiophene groups twisted out of the molecular plane, precluding close molecular π-stacking. Electrochemical investigations revealed two redox processes corresponding to interconversion between neutral, monoanionic and dianionic species for 3, analogous to 2. Oxidation of 0.1 mM [3]− in CH3CN was shown to give a green molecular film of 3 which, in contrast to as-prepared crystals of 3, showed significant conductivity. Electrochemical polymerisation of 3 carried out at different concentrations resulted in films; electrochemical, SNIFTIRS and UV-Vis results were consistent with incorporation of the intact metal dithiolene complex in these films. In contrast, electrochemical polymerisation of 2 gave a film charateristic of a polymerised thiophene but with no evidence of incorporation of the intact metal dithiolene complex. Copolymerisation of 3 with thiophene gave a gold-coloured electropolymerised film of significant conductivity that, upon dissolution in CH2Cl2, showed the characteristic low energy absorption of the Ni-dithiolene complex, confirming its incorporation. This copolymerisation approach offers a versatile route to the synthesis of metal dithiolene–polythiophene hybrid films.

Synthesis, electrochemical properties and electropolymerization studies on 3-thienyl substituted tetrathiafulvalenes. Single-crystal X-ray structure of 4,4′,5,5′-tetrakis-(3-thienyl)-tetrathiafulvalene

Abstract 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.

Synthesis, physical properties and X-ray crystal structures of a series of nickel complexes based on n-alkylthio-substituted ethylene-1,2-dithiolene ligands

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.

4,4′,5,5′-Tetrakis(2-thienyl)tetrathiafulvalene [TT-TTF]: synthesis and first X-ray crystal structure of a thiophene-substituted TTF electron donor

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.

Preparation and X-ray crystal structure of [Ni(dpdt)2], a novel nickel 1,2-dithiolene complex (H2dpdt=6-methylene-1,4-dithiepin-2,3-dithiol)

Abstract [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.

Third order NLO properties of PMMA films co-dispersed with metal dithiolene oligomers

Abstract Metal dithiolene oligomers show enhanced third order NLO properties compared with films containing monomeric metal complexes.

Soluble nickel bis(dithiolene) oligomers for third-order non-linear optical studies

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.

Increased delignification by white rot fungi after pressure refining Miscanthus

Pressure refining, a pulp making process to separate fibres of lignocellulosic materials, deposits lignin granules on the surface of the fibres that could enable increased access to lignin degrading enzymes. Three different white rot fungi were grown on pressure refined (at 6 bar and 8 bar) and milled Miscanthus. Growth after 28 days showed highest biomass losses on milled Miscanthus compared to pressure refined Miscanthus. Ceriporiopsis subvermispora caused a significantly higher proportion of lignin removal when grown on 6 bar pressure refined Miscanthus compared to growth on 8 bar pressure refined Miscanthus and milled Miscanthus. RM22b followed a similar trend but Phlebiopsis gigantea SPLog6 did not. Conversely, C. subvermispora growing on pressure refined Miscanthus revealed that the proportion of cellulose increased. These results show that two of the three white rot fungi used in this study showed higher delignification on pressure refined Miscanthus than milled Miscanthus.

Developments in the chemistry of sulphur-donor ligands

Abstract 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.

Preparation, properties and crystal structures of new nickel(II) complexes of 1,2-asymmetrically substituted dithiolenes for third-order non-linear optical applications

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.