Thies Thiemann

Paired electrosynthesis: micro-flow cell processes with and without added electrolyte

Abstract The thin layer flow cell geometry with working and auxiliary electrodes directly facing each other, allows electrosynthetic processes to be conducted in flow-through mode. At sufficiently small cell height, the two diffusion layers of working and auxiliary electrode overlap or become ‘coupled’. As a result electro-generated acids or bases are instantaneously neutralised, products from anode and cathode can interact, and, more importantly, bulk electrolysis is possible without intentionally added electrolyte. In this preliminary report, the operation of a micro-flow cell with coupled diffusion layers is demonstrated for the one electron oxidation of ferrocene and for the two electron–two proton reduction of tetraethyl ethylenetetracarboxylate dissolved in ethanol. In proof-of-principle bulk electrolysis experiments without intentionally added electrolyte, high yields of the product, tetraethyl ethanetetracarboxylate are obtained at a nickel working electrode. It is demonstrated that a sufficient concentration of electrolyte for bulk electrolysis is generated locally and in situ between working and auxiliary electrode.

Highly dichroic benzo-2,1,3-thiadiazole dyes containing five linearly π-conjugated aromatic residues, with fluorescent emission ranging from green to red, in a liquid crystal guest–host system

A number of fluorescent benzothiadiazole dyes have been synthesised and their optical properties, when dispersed in a liquid crystal host phase, examined. These dyes have five linearly π-conjugated aromatic ring systems (both with and without ethene and 1,3-butadiene spacers). The liquid crystalline host medium, used was the nematic phase of MLC-2039. The emission colours observed ranged from green to red, depending on the unsaturated chains attached at the 4- and 7- positions of the bezo-2,1,3-thiadiazole core. A highly dichroic and efficient fluoresence was observed. The dye 4,7–bis[5-bis(phenylethenyl)thiophen-2-yl]-2,1,3-benzothiadiazole is of particular importance. This is the first example of a dye emitting strong red fluorescence (633 nm). When dispersed in MLC-2039, dichroic ratio values up to 12.3 were obtained.

Spectroscopic (FT-IR, FT-Raman), first order hyperpolarizability, NBO analysis, HOMO and LUMO analysis of 2,4-bis(2-methoxyphenyl)-1-phenylanthracene-9,10-dione by ab initio HF and density functional methods

Anthraquinone derivatives are most important class of a system that absorb in the visible region. In this work, the vibrational spectral analysis was carried out using FT-IR and FT-Raman spectroscopy for 2,4-bis(2-methoxyphenyl)-1-phenylanthracene-9,10-dione. Theoretical calculations were performed by ab initio HF and DFT methods using 6-31G(*) basis set. The complete vibrational assignments of wavenumbers were made on the basis of potential energy distribution. The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. The calculated geometrical parameters (DFT) are in agreement with that of similar derivatives. The calculated first hyperpolarizability of the title compound is 4.69×10(-30) esu, which is 36.08 times that of urea and the title compound and the series of compounds it represents are attractive candidates for further studies in non linear optical applications.

Synthesis and biological evaluation of two new radiolabelled estrogens: [125I](E)-3-methoxy-17α-iodovinylestra-1,3,5(10),6-tetraen-17β-ol and [125I](Z)-3-methoxy-17α-iodovinylestra-1,3,5(10),6-tetraen-17β-ol

The synthesis of two novel radiolabelled estrogen derivatives, [125I](E)-3-methoxy-17alpha-iodovinylestra-1,3,5(10),6-tetraen-17beta-ol (E[125I]IVDE) and [125I](Z)-3-methoxy-17alpha-iodovinylestra-1,3,5(10),6-tetraen-17beta-ol (Z[125I]IVDE), was carried out aiming to study the influence of the introduction of a C6-C7 double bond on the biological properties of the estradiol molecule. 3-Methoxyestra-1,3,5(10),6-tetraen-17-one was synthesised starting from a suitably protected estrone and subsequently converted into the 17alpha-ethynyl derivative. The radioiodinated derivatives were stereoselectively formed by radioiododestannylation of the corresponding tributylstannyl precursors. The biodistribution of the novel [125I]iodovinylestradiol derivatives was evaluated in immature female mice. Biological data indicated that the Z-isomer, owing to its higher in vivo uptake by the target tissue, has the preferable configuration for further development of similar compounds for estrogen receptor detection.

Zn dust mediated reductive debromination of tetrabromobisphenol A (TBBPA)

Zinc dust/sodium hydroxide/ammonium formate system is highly effective for the debromination of the ubiquitous pollutant tetrabromobisphenol A (TBPPA) to bisphenol A (BPA). Treatment of pure TBPPA with NaOH or with another alkali hydroxide in the presence of ammonium formate in an alcohol at elevated temperatures (78-116 degrees C) leads to a successful debromination. An almost quantitative removal of TBBPA can be achieved.

Sonoelectrochemical effects in electro-organic systems.

This paper describes recent studies in organic sonoelectrochemistry at Coventry University, including the oxidation of thiophene monoxides, degradation of dye pollutants, formation of conducting polymers and electrosynthetic modification of proteins.

Detection of the damage caused to DNA by a thiophene-S-oxide using an electrochemical DNA-biosensor

The electrochemistry of 3,4-dibenzyl-2,5-dimethylthiophene-S-oxide was investigated as well as its interaction with dsDNA. The electrochemical study of the thiophene-S-oxide was performed at different pH values, in a mixed solvent and by solid state voltammetry, and showed that the molecule is reduced at a very negative potential, and the reduction is pH dependent. A glassy carbon electrode modified with a thick thiophene-S-oxide+dsDNA mixture was used to study the interaction of thiophene-S-oxide in situ with dsDNA at a charged interface. The experimental results give strong evidence that the reduced thiophene-S-oxide interacts with dsDNA causing damage with possible strand break and that the thiophene-S-oxide adduct formed with dsDNA can still undergo reduction.

Regiodirected substitution of [2.2]paracyclophanedienes and [2.2]paracyclophanes through tricarbonylchronium complexation

Abstract 4,7-dialkoxy[2.2]paracyclophanes and the corresponding 1,9-dienes are shown to undergo selective conplexation with Cr(CO) 3 L 3 -reagent on their less substituted benzene moiety. Lithiation/silytion of these complexes leads to arene- or bridge-substitution, respectively. An analagous behaviour is observed for the tricarbonylchromium[2.2]paracyclophane and its 1,9-diene.

Reductive degradation of tetrabromobisphenol A (TBBPA) in aqueous medium

Raney Ni–Al alloy in a dilute alkaline aqueous solution has shown to be a powerful reducing agent and is highly effective for the hydrodebromination of tetrabromobisphenol A (TBPPA) to bisphenol A (BPA) and other debrominated alicyclic compounds. The C–C bond of bisphenol A is cleaved easily under the reaction conditions. An almost quantitative removal of TBBPA can be attained at 90 °C.

Benzo-2,1,3-thiadiazole-based, highly dichroic fluorescent dyes for fluorescent host?guest liquid crystal displaysElectronic supplementary information (ESI) available: general experimental details and synthesis methods for compounds 4, 6, 7, 8, 10, 11 and 12. See http://www.rsc.org/suppdata/jm/b4/b402645d/

The highly dichroic fluorescent dyes 4,7-bis(p-alkoxyphenyl)-, 4,7-bis(p-alkoxymethylphenyl)-, and 4,7-bis(p-alkoxycarbonylphenyl)-2,1,3-benzothiadiazoles have been synthesized and their dichroic properties evaluated. A solution of the former dye dispersed in the commercial liquid crystalline MLC-2039 host phase showed a dichroic ratio value for fluorescence up to 9.1.