Effects of Number and Position of Meta and Para Carboxyphenyl Groups of Zinc Porphyrins in Dye-Sensitized Solar Cells: Structure–Performance Relationship

Porphyrin sensitizers containing <i>meta</i>- and <i>para</i>-carboxyphenyl groups in their meso positions have been synthesized and investigated for their performance in dye-sensitized solar cells (DSSCs). The superior performance of para-derivative compared to meta-derivative porphyrins was revealed by optical spectroscopy, electrochemical property measurements, density functional theory (DFT) calculations, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, incident photon-to-current conversion efficiency (IPCE), electrochemical impedance spectroscopy (EIS), and stability performance. Absorption spectra of <i>para</i>-carboxyphenyl-substituted porphyrins on TiO₂ show a broader Soret band compared to <i>meta</i>-carboxyphenyl-substituted porphyrins. ATR-FTIR spectra of the studied porphyrins on TiO₂ were applied to investigate the number and mode of carboxyl groups attached to TiO₂. The <i>V</i>_OC, <i>J</i>_SC, and IPCE values of para-series porphyrins were distinctly superior to those of meta-series porphyrins. The Nyquist plots of the studied porphyrins show that charge injection in para-series porphyrins is superior to that in meta-series porphyrins. The orthogonally positioned para derivatives have more efficient charge injection and charge transfer over charge recombination, whereas the efficiencies of flat-oriented meta derivatives are retarded by rapid charge recombination. Photovoltaic measurements of the studied <i>meta</i>- and <i>para</i>-carboxyphenyl-functionalized porphyrins show that the number and position of carboxyphenyl groups play a crucial role in the performance of the DSSC. Our results indicate that <i>para</i>-carboxyphenyl derivatives outperform <i>meta</i>-carboxyphenyl derivatives to give better device performance. This study will serve as a guideline for the design and development of organic, porphyrin, and ruthenium dyes in DSSCs

Formation of a Sulfur-Atom-Inserted N-Confused Porphyrin Iron Nitrosyl Complex by Denitrosation and C<i>−</i>S Bond Cleavage of an <i>S-</i>Nitrosothiol

The reaction of nitrosothiol, Ph3CSNO, with a divalent iron N-confused porphyrin complex, Fe(HCTPPH)Br, yields a {Fe(NO)}6 iron nitrosyl complex with a sulfur atom inserted in the Fe−C bond. The crystal structure reveals a bent Fe−N−O geometry and an η2-(C,S) bonding mode between iron and the C−S bond. A reaction mechanism involving a transnitrosation and a nitrosothiol C−S bond cleavage is proposed

Enhancing the Regioselectivity of B(C₆F₅)₃‑Catalyzed Epoxide Alcoholysis Reactions Using Hydrogen-Bond Acceptors

Epoxide alcoholysis is extensively employed in the synthesis of polymers and chemical intermediates, and it generally requires an acid catalyst for high rates and selectivity. Tris­(pentafluorophenyl)­borane [B­(C6F5)3] is among few catalysts that are selective to primary alcohol products of terminal aliphatic epoxides that do not possess any directing groups. We have previously observed that under many conditions, the reaction regioselectivity increases with conversion. Here, we confirm a prediction from our earlier computational model, and we experimentally demonstrate that this increase is due to a selectivity-enhancing role of the reaction products. We then show that deliberate addition of catalytic amounts of certain diols increases the reaction regioselectivity. Cis-1,2 or 1,3-diols are required to enhance selectivity, consistent with a mechanism where extended hydrogen-bonding networks preferentially organize the reactants. This work presents a route to tune regioselectivity without altering the catalyst backbone and provides another example of the role of H-bonding networks in reactions taking place in protic media

Enhancing the Regioselectivity of B(C₆F₅)₃‑Catalyzed Epoxide Alcoholysis Reactions Using Hydrogen-Bond Acceptors

Epoxide alcoholysis is extensively employed in the synthesis of polymers and chemical intermediates, and it generally requires an acid catalyst for high rates and selectivity. Tris­(pentafluorophenyl)­borane [B­(C6F5)3] is among few catalysts that are selective to primary alcohol products of terminal aliphatic epoxides that do not possess any directing groups. We have previously observed that under many conditions, the reaction regioselectivity increases with conversion. Here, we confirm a prediction from our earlier computational model, and we experimentally demonstrate that this increase is due to a selectivity-enhancing role of the reaction products. We then show that deliberate addition of catalytic amounts of certain diols increases the reaction regioselectivity. Cis-1,2 or 1,3-diols are required to enhance selectivity, consistent with a mechanism where extended hydrogen-bonding networks preferentially organize the reactants. This work presents a route to tune regioselectivity without altering the catalyst backbone and provides another example of the role of H-bonding networks in reactions taking place in protic media