Influence of pyrimidine additives in electrolytic solution on dye-sensitized solar cell performance

The influence of pyrimidine additives on the performance of a bis(tetrabutylammonium)cis-bis(thiocyanato)bis(2,2′-bipyridine-4-carboxylic acid, 4′-carboxylate)ruthenium(II) dye-sensitized TiO₂ solar cell with an I⁻/I₃⁻ redox electrolyte in acetonitrile was studied. The current–voltage characteristics were measured for more than 10 different pyrimidine derivatives under AM 1.5 (100 mW/cm²). The pyrimidine additives tested had varying effects on the performance of the cell. The additives drastically enhanced the open-circuit photovoltage (V_oc) and the solar energy conversion efficiency (η), but usually reduced the short circuit photocurrent density (J_sc) of the solar cell. Physical and chemical properties of the pyrimidines were computationally calculated in order to determine the reasons for the additive effects on cell performance. Consequently, the greater the calculated partial charge of the nitrogen atoms in the pyrimidine groups, the larger the V_oc but the smaller the J_sc values. The V_oc of the cell also increased as the ionization energy of the pyrimidine molecules decreased. Moreover, as the calculated dipole moment of the pyrimidine derivatives increased, the J_sc value was reduced, but the V_oc value was enhanced. These results suggest that the electron donicity of pyrimidine additives influenced the interaction with TiO₂ electrode and I⁻/I₃⁻ electrolyte, which lead to the changes in dye-sensitized solar cell performance.     

Preparation of macroreticular chelating resins containing mercapto groups from 2,3-epithiopropyl methacrylate/divinylbenzene copolymer beads and their adsorption capacity

Macroreticular chelating resins containing mercapto groups were prepared by the reaction of 2,3-epithiopropyl methacrylate/divinylbenzene macroreticular copolymer beads with ethanolic potassium hydrogensulfide solution for 1 h at 50°C. The adsorption capacities of this resin for Ag⁺, Hg²⁺, Pb²⁺ and Cd²⁺ were determined at various pH values. In the acidic region, the resin shows a high affinity for Ag⁺ and Hg²⁺ and high resistance against air oxidation. Cadmium is readily eluted with 1 mol dm^?3 hydrochloric acid; silver, mercury and copper ions can be eluted with 1 mol dm^?3 hydrochloric acid containing 5% (w/v) thiourea. The proposed resin appears to be useful for the removal of As³⁺ from aqueous solutions.     

Novel synthesis of N-alkyl-3,4-disubstituted pyrrolidine-2,5-diones: Condensation of α-oxoketene O,N-acetals and maleic anhydride

A novel method for the synthesis of N-alkyl-3-acyl-4-alkoxycarbonylmethylpyrrolidine-2,5-diones (3) was accomplished. α-Oxoketene O,N-acetals (1) reacted with maleic anhydride (2) at 80–110 °C for 5 h without solvent to give 3 in moderate to good yield (36–74%). Single X-ray crystallographic analysis showed that the two substituents on C-3 and C-4 were trans.     

Synthesis of trifluoromethylated pyrido[2,3‐d]pyrimidine‐2,4‐diones from 6‐aminouracils and trifluoromethylated pyrazolo[3,4‐b]‐pyridines from 5‐aminopyrazoles

5 or 7‐Trifluoromethyl‐1,2,3,4‐tetrahydropyrido[2,3‐d]pyrimidine‐2,4‐diones 3 , 5 , 10 , 13 and 4‐ or 6‐trifluoromethylpyrazolo[3,4‐b]pyridines 15 , 16 , 19 , 21 were prepared from 6‐aminouracils and 5‐aminopyrazoles, respectively, in good yields by the use of building blocks such as 4,4,4‐trifluoro‐1‐phenyl‐1,3‐butanedione, 1,1,1‐trifluoro‐4‐phenyl‐3‐buten‐2‐one, 4‐ethoxy‐1,1,1‐trifluoro‐3‐buten‐2‐one, and ethyl trifluoroacetoacetate.     

Spectroelectrochemical studies on mixed-valence states in a cyanide-bridged molecular square, [Ru(II)(2)Fe(II)(2)(mu-CN)(4)(bpy)(8)](PF6)(4).CHCl(3).H(2)O

A cyanide-bridged molecular square of [Ru(II) (2)Fe(II) (2)(mu-CN)(4)(bpy)(8)](PF(6))(4).CHCl(3).H(2)O, abbreviated as [Ru(II) (2)Fe(II) (2)](PF(6))(4), has been synthesised and electrochemically generated mixed-valence states have been studied by spectroelectrochemical methods. The complex cation of [Ru(II) (2)Fe(II) (2)](4+) is nearly a square and is composed of alternate Ru(II) and Fe(II) ions bridged by four cyanide ions. The cyclic voltammogram (CV) of [Ru(II) (2)Fe(II) (2)](PF(6))(4) in acetonitrile showed four quasireversible waves at 0.69, 0.94, 1.42 and 1.70 V (vs. SSCE), which correspond to the four one-electron redox processes of [Ru(II) (2)Fe(II) (2)](4+) right arrow over left arrow [Ru(II) (2)Fe(II)Fe(III)] (5+) right arrow over left arrow [Ru(II) (2)Fe(III) (2)](6+) right arrow over left arrow [Ru(II)Ru(III)Fe(III) (2)](7+) right arrow over left arrow [Ru(III) (2)Fe(III) (2)](8+). Electrochemically generated [Ru(II) (2)Fe(II)Fe(III)](5+) and [Ru(II) (2)Fe(III) (2)](6+) showed new absorption bands at 2350 nm (epsilon =5500 M(-1) cm(-1)) and 1560 nm (epsilon =10 500 M(-1) cm(-1)), respectively, which were assigned to the intramolecular IT (intervalence transfer) bands from Fe(II) to Fe(III) and from Ru(II) to Fe(III) ions, respectively. The electronic interaction matrix elements (H(AB)) and the degrees of electronic delocalisation (alpha(2)) were estimated to be 1090 cm(-1) and 0.065 for the [Ru(II) (2)Fe(II)Fe(III) (2)](5+) state and 1990 cm(-1) and 0.065 for the [Ru(II) (2)Fe(III) (2)](6+) states.     

Synthesis of 3-sulfanylpropanols containing three consecutive stereocenters via tandem Michael-aldol reaction of enoylthioamides with acetals as key reaction

(2S,3S,1′R)-2-(α-Methoxybenzyl)-3-phenyl-3-sulfanylpropionamides were diastereoselectively prepared by the reactions of N-cinnamoyl-4S-isopropyl-5,5-dimethyloxazolidinethione with acetals in the presence of SnCl₄. The absolute configuration of the three newly created contiguous stereocenters was determined by the X-ray analysis of the disulfide. The amides were transformed into propanols by the reductive removal of the oxazolidinone moiety.     

Solar hydrogen production. Significant effect of Na2CO3 addition on water splitting using simple oxide semiconductor photocatalysts

Recent progress in photocatalytic decomposition of water to H₂ and O₂ using simple oxide semiconductor catalysts has been reviewed. Addition of Na₂CO₃ to Pt/TiO₂ suspension in water enhanced the stoichiometric decomposition significantly. This Na₂CO₃ addition method has been proved to be very useful to accelerate water splitting over various kinds of oxide semiconductor photocatalysts. The role of CO₃ ^2? anion on the acceleration of water splitting was clarified. Finally, it was firstly demonstrated in the world that water was decomposed efficiently and stoichiometrically to H₂ and O₂ using a 3 wt% NiOx/TiO₂ photocatalyst under real solar light irradiation in Tsukuba, Japan by this Na₂CO₃ addition method.