Organophotocatalytic Aerobic Oxygenation of Phenols in a Visible-Light Continuous-Flow Photoreactor

A mild photocatalytic phenol oxygenation enabled by a continuous-flow photoreactor using visible light and pressurized air is described herein. Products for wide-ranging applications, including the synthesis of vitamins, were obtained in high yields by precisely controlling principal process parameters. The reactor design permits low organophotocatalyst loadings to generate singlet oxygen. It is anticipated that the efficient aerobic phenol oxygenation to benzoquinones and p-quinols contributes to sustainable synthesis.     

Improvement of ZnO nanorod based quantum Dot (cadmium sulfide) sensitized solar cell efficiency by aluminum doping

This study investigates the performance of quantum dot sensitized solar cells (QDSSCs) based on aluminum (Al)-doped and undoped ZnO nanorods. Current density–voltage (J–V) characterization shows that Al doping into ZnO nanorods (AZO NRs) can improve short circuit current density (J_sc) and the energy conversion efficiency (η) of QDSSCs. The maximum η=1.15% is achieved in QDSSCs when Al concentration is 0.5 wt%, as compared to undoped state where η=0.57%. These current densities and the energy conversion efficiency improvement are studied using the electrochemical impedance spectroscopy (EIS). EIS results indicate that the electron transport resistance in the photoanode of QDSCs is reduced with introduction of Al into ZnO structure, which leads to increasing J_sc. It is also found that recombination resistance reduces with introduction of Al into ZnO because of the upward displacement of Fermi level with respect to AZO conduction band (CB) and increasing electron density in the ZnO CB. This reduction of recombination resistance causes higher recombination rate in QDSCs based AZO NRs.     

The suzuki–heck polymerization as a tool for the straightforward obtainment of poly(fluorenylene‐vinylene) sensitizers for dye‐sensitized solar cells

This article describes the synthesis and properties of the first poly(arylene‐vinylene)‐based sensitizers for application in dye‐sensitized solar cells (DSSC). The polymers were prepared by the Suzuki–Heck copolymerization of potassium vinyltrifluoroborate (PVTB) with a mixture of dibromoaryl comonomers designed to obtain macromolecules able to bind onto the photoelectrode by means of carboxyphenylene units. The copolymerization reactions were carried out in the presence of an excess of PVTB to lower the molecular weights of the polymers, which were obtained as soluble materials. The polymers poly[(9,9‐didodecyl‐2,7‐fluorenylene)‐vinylene‐co‐(carboxy‐2,5‐phenylene)‐vinylene] ( P1 ), poly[(9,9‐didodecyl‐2,7‐fluorenylene)‐vinylene‐co‐(carboxy‐2,5‐phenylene)‐vinylene‐co‐(4,7‐benzothiadiazolylene)‐vinylene] ( P2 ), and poly[(9,9‐didodecyl‐2,7‐fluorenylene)‐vinylene‐co‐(carboxy‐2,5‐phenylene)‐vinylene‐co‐2,5‐thienylene‐vinylene] ( P3 ) were used in DSSC devices, obtaining conversion efficiencies up to 0.88% ( P3 ). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Triarylamine-Functionalized Ru Dyes with Different Conjugation Lengths for Highly Efficient Dye Sensitized Solar Cells

Triarylamine-functionalized ruthenium (Ru) complexes with different conjugation linkage lengths are synthesized and applied to dye-sensitized solar cells (DSSCs). These triarylamine-functionalized Ru complexes show appreciably high extinction coefficients. DSSCs based on the new dye show higher power conversion efficiency than standard N3 dyes under same conditions. Among others, Ru-TP3 dye that has the longest conjugation length shows the highest efficiency of 3.7% under simulated 1 sun illumination (AM 1.5).     

A One-Pot Approach to Novel Pyridazine C-Nucleosides

The synthesis of glycosides and modified nucleosides represents a wide research field in organic chemistry. The classical methodology is based on coupling reactions between a glycosyl donor and an acceptor. An alternative strategy for new C-nucleosides is used in this approach, which consists of modifying a pre-existent furyl aglycone. This approach is applied to obtain novel pyridazine C-nucleosides starting with 2- and 3-(ribofuranosyl)furans. It is based on singlet oxygen [4+2] cycloaddition followed by reduction and hydrazine cyclization under neutral conditions. The mild three-step one-pot procedure leads stereoselectively to novel pyridazine C-nucleosides of pharmacological interest. The use of acetyls as protecting groups provides an elegant direct route to a deprotected new pyridazine C-nucleoside.     

Molecular design of corrole‐based D‐π‐A sensitizers for dye‐sensitized solar cell applications

First principles calculations based on density functional theory (DFT) have been performed to design a new set of donor‐corrole‐bridge‐acceptor type systems based on the gallium corroles for dye‐sensitized solar cell applications. The design strategy for these systems is based on the benchmark studies done on the experimentally tested aluminum, gallium, and tin metallocorroles. Unfortunately, corrole analogues display poor light to current conversion efficiencies in spite of their desirable photophysical properties. Thus, improving the efficiency of corrole analogues has become a major challenge and ways to identify solutions to this is of outstanding fundamental importance. This study shows the lack of charge directionality toward anchoring group as plausible reason for the poor efficiencies of reported corrole systems, which enabled us to fine‐tune the electronic and optical properties of new D‐π‐A type systems, COR1‐COR4. The molecular geometries, electronic structure, and binding orientation of these systems on TiO₂ surface were investigated using DFT, TD‐DFT, and PBC methods. When compared with the reported corroles, COR1‐COR4 have a smaller band gaps, red‐shifted absorption spectra with higher extinction coefficients (10⁵ M^?1 cm^?1) and improved nonlinear optical properties. Importantly, results revealed that these dyes bind with two‐arm mode to TiO₂ surface and the density of states of the dye@TiO₂ elucidate strong coupling between the dyes and TiO₂ surface. We anticipate that the unique photophysical properties of these sensitizers will trigger the experimental efforts to yield a new generation of sensitizers based on corrole macrocyle. © 2015 Wiley Periodicals, Inc.