A series of new pyrido [3,4-b]pyrazine-based organic sensitizers (PP-I and APP-I-IV) containing different donors and p-spacers have been synthesized and employed in dye-sensitized solar cells (DSSCs). The absorption spectra properties of dyes are analysed by density functional theory (DFT). The calculated results in combination with the experiments suggest that the absorption characteristics and excited state features will mainly be dominated by charge transfer transitions from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) and to higher LUMO orbitals.Furthermore, attaching the octyloxy groups significantly extends the p-conjugation of the donor in APP-IV, which raises the HOMO energy and facilitates its oxidation. As a consequence, APP-IV exhibits the lowest HOMO-LUMO energy gap among all dyes, which, in turn, corresponds well with the red shift of the absorption spectra. Transient photovoltage and photocurrent decay experiments as well as electrochemical impedance spectroscopy indicate that the electron lifetime and charge recombination resistance are increased due to the introduction of octyloxy chains on the donor unit, resulting in the high photovoltage based on APP-IV. It was found that APP-IV based DSSCs with liquid electrolyte display the highest power conversion efficiency (PCE) of 7.12%. Importantly, a PCE of 6.20% has been achieved for APP-IV based DSSCs with ionic-liquid electrolytes and retained 97% of the initial value after continuous light soaking for 1000 h at 60 C. This renders these pyrido [3,4-b]pyrazine-based sensitizers quite promising candidates for highly efficient and stable DSSCs.

In this work, six new D-A-π-A sensitizers (ID1-ID6), with triarylamine as the electron donor; isoindigo as a auxiliary electron withdrawing unit; thiophene, furan, and benzene as the linker; and cyanoacrylic acid as the anchoring group, were synthesized through simple synthetic procedures and with low cost. Their absorption spectra were broad with long wavelength absorption maximum approximately at 589 nm and the absorption onset at 720 nm on the TiO(2) film. Electrochemical experiments indicate that the HOMO and LUMO energy levels can be conveniently tuned by alternating the donor moiety and the linker. All of these dyes performed as sensitizers for the DSSCs test under AM 1.5 similar experimental conditions, and a maximum overall conversion efficiency of 5.98% (J(sc) = 14.77 mA cm(-2), V(oc) = 644 mV, ff = 0.63) is obtained for ID6-based DSSCs when TiO(2) films were first immersed for 6 h in 20 mM CDCA ethanol solution followed by 12 h of dipping in the dye CH(2)Cl(2) solution. Electrochemical impedance measurement data implies that the electron lifetime can be increased by coadsorption of CDCA, which leads to a lower rate of charge recombination and thus improved V(oc).

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Two new benzotriazole-bridged sensitizers are designed and synthesized (BTA-I and BTA-II) containing a furan moiety for dye-sensitized solar cells (DSSCs). Two corresponding dyes (BTA-III and BTA-IV) with a thiophene spacer were also synthesized for comparison. All of these dyes performed as sensitizers for DSSCs, and the photovoltaic performance data of these benzotriazole-bridged dyes showed a high open-circuit voltage (V(oc): 804-834 mV). Among the four dyes, DSSCs based on BTA-II, with a furan moiety and branched alkyl chain, showed the highest V(oc) (834 mV), a photocurrent density (J(sc)) of 12.64 mA cm(-2), and a fill factor (FF) of 0.64, corresponding to an overall conversion efficiency (η) of 6.72%. Most importantly, long-term stability of the BTA-I-IV-based DSSCs with ionic-liquid electrolytes under 1000 h light-soaking was demonstrated, and BTA-II exhibited better photovoltaic performance of up to 5.06% power conversion efficiency.

Sulfinamides were synthesized from sulfonyl chlorides using a procedure involving the in situ reduction of sulfonyl chlorides. The reaction is broad in scope and easy to perform.Sulfinamides, especially chiral sulfinamides, play vital roles in the modern asymmetric chemistry. 1 Furthermore, sulfinamides can also act as N-sulfinyl protecting group in ease of removal under mild conditions. 2 Even though there are various procedures reported for the preparation of sulfinamides from sulfinic acids 3 , sulfinates 4 , sulfinyl chlorides 5 , disulfides 6 , and homolytic substitution at the sulfur atom 7 , these reactions often require two or more synthetic steps. A one-step process would be useful and increase the exploration of sulfinamide chemistry.Sulfinamides are useful compounds and can be transformed to a number of other important functional groups. 8 For example, they can be converted to sulfonimidoyl chlorides, whose chemistry is both interesting and useful. 9 We reported that benzothiazines can be prepared from N-aryl sulfinamides by oxidation with t-butyl hypochlorite and subsequent treatment with an alkene or alkyne in the presence of a Lewis acid. (Scheme 1). 10 The requisite sulfinamide was prepared from a sulfinyl choride in high yield. While sulfinyl chlorides are not exceptionally difficult to make, they are sensitive to hydrolysis and require preparation using noxious reagents such as thionyl chloride. We thought that a procedure to quickly access sulfinamides would be useful in both exploring sulfinamide chemistry and derivatives such as sulfonimidoyl chlorides.A number of years ago Sharpless 11 reported the synthesis of sulfinate esters from sulfonyl chlorides by a one-pot reductive esterification reaction using either phosphites as the reducing agent. Attempts to prepare sulfinamides by the Sharpless group were not successful. We thought however, that the modification of the synthesis of sulfinate esters introduced by Toru 12 , which used triarylphophines as the reductant, would be suitable for the synthesis of such compounds. This letter reports the realization of that idea.We began our studies by simply using Toru's procedure for sulfinate ester formation. 11 The results are summarized in Table 1. When a CH 2 Cl 2 solution of triphenylphosphine was added to the mixture of TsCl, TEA (10 equivalents) and BzNH 2 in CH 2 Cl 2 at 0 °C, only sulfonamide 6 and PPh 3 were detected by the NMR analysis of the crude mixture (entry 1). However, a small change in the addition sequence offered an encouraging result. When PPh 3 and benzylamine in CH 2 Cl 2 were added to a mixture of triethylamine and tosyl chloride, the desired HarmataM@Missouri.edu. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript sulfinamide was isolated in 62% yield, (entry 2). Only a 14% yield of sulfinamide, accompanied by 40% sulfonamide, was isolated when the reaction was performed by the addition of PPh 3 to TsCl in CH 2 Cl 2 over 1 hour followed by addition of a mixture of BzNH 2 and T...

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Sugars produced from photosynthesis in leaves are transported through the phloem tissues within veins and delivered to non-photosynthetic organs, such as roots, stems, flowers, and seeds, to support their growth and/or storage of carbohydrates. However, because the phloem is located internally within the veins, it is difficult to access and to study the dynamics of sugar transport. Radioactive tracers have been extensively used to study vascular transport in plants and have provided great insights into transport dynamics. To better study sucrose partitioning in vivo, a novel radioactive analog of sucrose was synthesized through a completely chemical synthesis route by substituting fluorine-18 (half-life 110 min) at the 6’ position to generate 6’-deoxy-6’[18F]fluorosucrose (18FS). This radiotracer was then used to compare sucrose transport between wild-type maize plants and mutant plants lacking the Sucrose transporter1 (Sut1) gene, which has been shown to function in sucrose phloem loading. Our results demonstrate that 18FS is transported in vivo, with the wild-type plants showing a greater rate of transport down the leaf blade than the sut1 mutant plants. A similar transport pattern was also observed for universally labeled [U-14C]sucrose ([U-14C]suc). Our findings support the proposed sucrose phloem loading function of the Sut1 gene in maize, and additionally demonstrate that the 18FS analog is a valuable, new tool that offers imaging advantages over [U-14C]suc for studying phloem transport in plants.