Quinoxalino[2,3-c]cinnolines and their 5-N-oxide: alkoxylation of methyl-substituted quinoxalino[2,3-c]cinnolines to acetals and orthoesters.

We report the alkoxylation of methyl-substituted quinoxalino[2,3-c]cinnolines to give acetals and orthoesters in high yields. Routes to the precursors of this alkoxylation reaction as well as other quinoxalino[2,3-c]cinnoline and their 5-oxide derivatives are reported. Most of these quinoxalino[2,3-c]cinnolines were prepared by cyclization of the corresponding 2-amino-3-(2-nitrophenyl)quinoxaline, which, in turn, result from an unusual Beirut reaction from benzofurazan oxides plus 2-nitrobenzylcyanides. Mechanistic explanations for these intriguing reactions are presented.

High photo-currents with a zwitterionic thiocyanate-free dye in aqueous-based dye sensitized solar cells.

We report a new water soluble and stable thiolate/disulfide redox couple (T(-)/DS) and its use with a new zwitterionic and thiocyanate-free dye (T169) in a 100% aqueous electrolyte system. A DSSC incorporating T169 and the T(-)/DS showed the highest photocurrents (Jsc = 13.30 mA cm(-2)) and IPCE% (84%) values reported to date. In addition, a 2000 h long-term stability measurement was performed, where Jsc and Voc of the above mentioned DSSC stayed somehow the same except for the fill factor (FF) which decreased from 0.62 to 0.48 and consequently lowered the total efficiency (from η = 4.5% on day 1 to η = 3.3% after 2000 h).

Universal low-temperature MWCNT-COOH-based counter electrode and a new thiolate/disulfide electrolyte system for dye-sensitized solar cells.

A new thiolate/disulfide organic-based electrolyte system composed of the tetrabutylammonium salt of 2-methyl-5-trifluoromethyl-2H-[1,2,4]triazole-3-thiol (S(-)) and its oxidized form 3,3'-dithiobis(2-methyl-5-trifluoromethyl-2H-[1,2,4]triazole) (DS) has been formulated and used in dye-sensitized solar cells (DSSCs). The electrocatalytic activity of different counter electrodes (CEs) has been evaluated by means of measuring J-V curves, cyclic voltammetry, Tafel plots, and electrochemical impedance spectroscopy. A stable and low-temperature CE based on acid-functionalized multiwalled carbon nanotubes (MWCNT-COOH) was investigated with our S(-)/DS, I(-)/I3(-), T(-)/T2, and Co(II/III)-based electrolyte systems. The proposed CE showed superb electrocatalytic activity toward the regeneration of the different electrolytes. In addition, good stability of solar cell devices based on the reported electrolyte and CE was shown.

Unusual Friedlander reactions: a route to novel quinoxaline-based heterocycles.

Acid catalyzed Friedlander reactions of a number of 2,3-dihydro-1H-cyclopenta[b]quinoxaline-1-ones with 2-aminobenzaldehyde yield, unexpectedly, 8H-indolo[3,2-a]phenazine and quinolino[2,3-c]cyclopentadienone[2,3-b]quinoxalines, the structures of derivatives of which were confirmed by X-ray crystallography. Easy routes to novel quinoxaline-based indoles, quinolones, and quinoxaline-1,4-dioxides are reported, and proposed mechanisms for the unexpected products are discussed.