Articles written in Journal of Chemical Sciences

    • Thiophene-bithiazole based metal-free dye as DSSC sensitizer: Effect of co-adsorbents on photovoltaic efficiency

      Jayanthy S Panicker Bijitha Balan Suraj Soman Tanwistha Ghosh Vijayakumar C Nair

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      A new molecule consisting of a bithiazole chromophore sandwiched between two thiophenes, functionalized with benzothiophene unit at one end and cyanoacrylic acid at the other end (BT1) was synthesized, photophysical properties were studied and employed as a photosensitizer in dye-sensitized solar cells (DSSCs). The molecule exhibited an intense absorption in the UV-visible region with absorption extending up to 500 nm. The ground and excited state potentials of BT1 were calculated to be 1.29 and -0.65 V, respectively vs. NHE using cyclic voltammetry. The ground state energy level is more positive than the triiodide electrolyte and excited state energy level is considerably more negative than the TiO2 satisfying the energetic requirements for a photosensitizer in DSSC. The solar cells fabricated from BT1 exhibited an efficiency of 1.13%. The effect of various co-adsorbents (CDCA, TP1 and TP2) on the DSSC performance was investigated in detail. In the presence of CDCA, the photovoltaic efficiency was enhanced to 1.25%, whereas, in the presence of TP1 and TP2, the efficiency lowered to 0.20% and 0.59%, respectively. The increased efficiency in the presence of CDCA could be attributed to the prevention of the aggregation of dye molecules induced by CDCA. On the other hand, TP1 and TP2 were found to be not as effective as CDCA to prevent aggregation leading to the lowering of photoconversion efficiency.

    • Reactivity of ynamides with AlCl3 and ICl: Ready access to (E)-achloroenamides and (E/Z)-a-chloro-b-iodo-enamides


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      AlCl3 acts as a chlorinating agent for ynamides in the presence of stoichiometric amount of water in the environmentally benign solvent dimethylcarbonate, affording efficient access to (E)-a-chloroenamides via hydrochlorination, with water as a protic source. The role of water in the reaction was proven by deuterium labelling experiment. Epoxy-ynamides undergo iodochlorination in addition to the cleavage of the epoxy ring to afford (E/Z)-a-chloro-b-iodo-enamides. Regio- and stereochemical assignments for the products are based on X-ray crystallographic studies.

      Chloroenamides are formed regio- and stereo-specifically via hydrochlorination of ynamides with AlCl3+H2O (1:1) in a dimethyl carbonate; aryl substituted epoxy ynamides afford (iodo)(chloro) enamides upon treatment with ICl.

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