Ronald E. Noftle

Studies of platinum electroplating baths Part III. The electrochemistry of Pt(NH3)4 − x(H2O)2+2 and PtCl4 − x(H2O)(2 − x)−x

Abstract The electrochemistry of the Pt(NH 3 ) 4 − x (H 2 O) 2+ x complexes ( x = 0−2) in an aqueous phosphate buffer was investigated. 195 Pt NMR was used to confirm that, in this medium, all are stable in solution even at 370 K. Moreover, their voltammetry shows that none is reduced at room temperature, although all give reduction peaks at above 353 K; a slow chemical change to the Pt(II) species (possibly displacement of NH 3 ligands by H 2 O) in solution is essential to produce the electroactive species. The magnitudes of the current densities are always much less than those expected for mass transport control and suggest that the rate of this chemical change increases along the series Pt(NH 3 ) 2+ 4 3 ) 3 (H 2 O) 2+ cis -Pt(NH 3 ) 2 (H 2 O) 2+ 2 . In contrast, the complexes PtCl 4 − x (H 2 O) (2 − x )− x in 1 M HClO 4 all show comparatively simple electrochemistry even at room temperature. Indeed, the complexes ( x = 2−4) show single reduction waves with mass transport-controlled plateaux and very similar half-wave potentials. Furthermore, 195 Pt NMR shows that displacement of chloride by water does occur, but only on the time-scale of many hours. The mechanism of these electrodeposition reactions, including the possible role of Pt(H 2 O) 2+ 4 , is discussed. Although the dissolution of K 2 PtCl 4 in water is a facile way to produce a readily reducible Pt(II) species, the presence of free chloride ion in solution leads to corrosion of substrates and this prevents the use of such solutions as practical electroplating baths.

Characterization and crystal structures of some fluorinated imides

Abstract The previously known, but not well-characterized, fluorinated imides, trifluoroacetyltrifluoroacetimide, HN(C(O)CF3)2 (1), acetyltrifluoroacetimide, HN(C(O)CH3)C(O)CF3 (2), and dichlorophosphoryltrifluoroacetimide, HN(P(O)Cl2)C(O)CF3 (3), have been shown to be moderately strong acids in aqueous solution; the first two compounds have pKa’s of 2.0 and 2.1 while the last compound consumes three equivalents of base per mole of imide owing to the hydrolyzable chlorine atoms. All three imides show a window of electrochemical inactivity on platinum from 0 to near +2.0 V. On vitreous carbon, (1) and (2) are inactive from –1.0 to +1.5 V and (3) from –1.0 to +1.0 V (vs. SCE). (1) crystallizes in a body-centered tetragonal unit cell while (2) and (3) crystallize in monoclinic unit cells. Hydrogen-bonded chains are formed in (1) and (2) and hydrogen-bonded dimers are formed in (3). The compounds were further characterized by 1H, 19F, and 13C NMR, FTIR, and elemental analysis.

High efficiency organic solar cells with spray coated active layers comprised of a low band gap conjugated polymer

Airbrush is a promising tool for large scale organic thin film deposition in photovoltaic devices fabrication. This paper reports a detailed study on solar cell performance using airbrush spray deposition for active layer composed with recently developed low band gap donor material poly[4,8-bis(1-pentylhexyloxy)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-2,1,3-benzoxadiazole-4,7-diyl and [6,6]-phenyl-C61-butyric acid methyl ester. The effect of carrier solvent and substrate temperature on film morphology are studied; a formula in 1,2-dichlorobenzene sprayed at a substrate temperature of 80 °C is found to be the optimum condition that produces a peak power conversion efficiency of 5.8%.

Preparation and properties of conducting polypyrrole doped with fluorinated imides

Abstract Doped polypyrrole is prepared electrochemically by oxidative polymerization of the monomer in aqueous solutions of the fluorinated imines, HN(SO 2 CF 3 ) 2 , HN(SO 2 CF 3 )C(O)CF 3 and HN(SO 2 F)C(O)CF 3 ; the conductivities of the free-standing films range from 3 to 22 S cm −1 . PPY +− N(SO 2 CF 3 ) 2 exhibits the expected semiconductor behaviour and is especially stable under ambient conditions in the laboratory. Polymerization of pyrrole also occurs in acetonitrile solution in the presence of the corresponding tetralkylammonium salts.

An interpretation of the formal potential for the ferricyanide / ferrocyanide couple as a function of solvent composition

The purpose of this paper is, however, to check the surprising results of Gutmann et al. and to suggest an alternative interpretation emphasising the conclusions important to studies in aqueous solution

Stoichiometric preference in copper-promoted oxidative DNA damage by ochratoxin A.

The ability of the fungal carcinogen, ochratoxin A (OTA, 1), to facilitate copper-promoted oxidative DNA damage has been assessed using supercoiled plasmid DNA (Form I)-agarose gel electrophoresis and gas chromatography-mass spectrometry with selected-ion monitoring (GC-MS-SIM). OTA is shown to promote oxidative cleavage of Form I DNA with optimal cleavage efficiency occurring under excess Cu(II) conditions. As the concentration of OTA was increased and present in excess of Cu(II) the cleavage was less effective. Parallel findings were found for the ability of the OTA-Cu mixture to facilitate oxidative base damage. Yields (lesions per 10(6) DNA bases) of modified bases upon exposure of calf-thymus DNA (CT-DNA) to OTA-H(2)O(2)-Cu(II) were diminished when the OTA:Cu ratio was increased to 5:1. Electrochemical studies carried out in methanol implicate a ligand-centered 2e oxidation of OTA in the presence of excess Cu(II), while product analyses utilizing electrospray mass spectrometry support the intermediacy of the quinone, OTQ (3), in Cu-promoted oxidation of OTA. The implications of these findings with regard to the mutagenicity of OTA are discussed.

Synthesis and characterization of thiophenes with fluorinated substituents

Abstract The synthesis of several 3-(polyfluoro)thiophenes, which are possible precursors to conductive polythiophenes, is described. This report includes an improved synthesis of 3-trifluoromethylthiophene and the previously reported but uncharacterized 3-fluoroformylthiophene. The new compounds 1-(3-thienyl)-1H,2H,3H,3H-nonafluorohept-1-ene, 1-(3-thienyl)-1H,2H,3H,3H-tridecafluoronon-1-ene, 1-(3-thenyl)-trifluoroacetate, 1-(3-thenyl)-heptafluorobutyrate, and 1-(3-thenyl)-3-fluorosulfuryltetrafluoroethylether are reported. The last compound is unstable and decomposes to 1-fluorosulfuryl-1-fluoroformyldifluoromethane and thenyl fluoride. More extensive data for the previously prepared 1-(3-thienyl)-1H,2H,2H,3H,3H-tridecafluoronon-1-ol and 1-(3-thienyl)-1H,2H,2H,3H,3H-nonafluoroheptan-1-ol are also included.

An efficient method for the synthesis of 3-alkylthiophenes bearing functional groups on the side chain: imides and amides

A method utilizing Rieke® zinc reagents is described for the synthesis of 5-(3-thienyl)pentanenitrile from which 5-(3-thienyl)-N-acetylpentanamide and 5-(3-thienyl)-N-(4-trifluoromethyl)benzoylpentaneamine have been prepared. A study of the effect of different catalysts on the product composition and extent of conversion has been carried out. The method should be widely applicable to the synthesis of 3-alkylthiophenes bearing functional groups on the side chain which have been rather difficult to prepare previously. The characterization and oxidative polymerization/oligomerization of the new compounds is described.

Exploring Spray-Coating Techniques for Organic Solar Cell Applications

We have investigated spray coating as a novel processing method for organic solar cell fabrication. In this work, spraying parameters and organic solvent influences have been correlated with cell performance. Using airbrush fabrication, bulk heterojunction photovoltaic devices based on a new low band gap donor material: poly[(4,8-bis(1-pentylhexyloxy)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-2,1,3-benzoxadiazole-4,7-diyl] with the C60-derivative (6,6)-phenyl C61-butyric acid methyl ester (PCBM) as an acceptor, have achieved power conversion efficiencies over 3%. We show that airbrush fabrication can be carried out with simple solvents such as pristine 1,2-dichlorobenzene. Moreover, the influence of device active area has been studied and the 1 cm2 device by spray coating maintained an excellent power conversion efficiency of 3.02% on average.

Investigation of the lifetimes of some pyrrole species by rapid scan cyclic voltammetry and double potential step techniques

The electrochemical oxidation of 1-(phenylsulfonyl)pyrrole (1), 3-t-butyl-1-(phenylsulfonyl)pyrrole (2), 3-t-butylpyrrole (3), and 1-(tris-(isopropyl)silyl)pyrrole (4) was investigated by fast-scan cyclic voltammetry and double potential step chronoamperometry. The electron transfer rate constants were obtained and the lifetimes of the radical-cations resulting from oxidation of (1–4) were estimated using the results of the double potential step experiments in conjunction with simulation techniques. All of the radical-cations have lifetimes less than 1 ms.