Excited State Geometries and Vertical Emission Energies of Solvated Dyes for DSSC: A PCM/TD-DFT Benchmark Study

The ability of Time-Dependent Density Functional Theory (TD-DFT) to provide excited state geometries and reproduce emission energies of organic D-π-A dyes designed for DSSC applications is evaluated. The performance of six functionals (CAM-B3LYP, MPW1K, ωB97X-D, LC-BLYP, LC-ωPBE, and M06-HF) in combination with three basis sets (cc-pVDZ, 6-31+G­(d,p), and 6-311+G­(2d,p)) has been analyzed. Solvent effects have been taken into account by means of a Polarizable Continuum Model in both LR and SS formalisms. Our LR-PCM/TD-DFT results show that accurate emission energies are obtained only when solvent effects are included in the computation of excited state geometries and when a range separated hybrid functional is used. Vertical emission energies are reproduced with a mean absolute error of at most 0.2 eV. The accuracy is further improved using the SS-PCM formalism

Stereoselective Synthesis of 3‑Substituted Tetra­hydro­pyrazino­iso­quinolines via Intramolecular Cyclization of Enantiomerically Enriched Dihydro‑2<i>H</i>‑pyrazines

The preparation of 3-substituted tetra­hydro­pyrazino­iso­quinolines using the tributyltin hydride mediated intramolecular radical cyclization of suitably protected 2-substituted 3,4-dihydropyrazines is reported. The compounds are obtained as single enantiomers, as the relative configuration of the new generated stereogenic center is driven by the stereochemistry of the 2-substituted carbon in the starting materials, which is in turn derived from naturally occurring amino acids

Correction to “Combining Dithienosilole-Based Organic Dyes with a Brookite/Platinum Photocatalyst toward Enhanced Visible-Light-Driven Hydrogen Production”

Correction to “Combining Dithienosilole-Based Organic Dyes with a Brookite/Platinum Photocatalyst toward Enhanced Visible-Light-Driven Hydrogen Production

imposte

The design, synthesis, and characterization of a new class of blue-colored thiophene-substituted Pechmann dyes are reported. Due to a distinguishing blue coloration and the capability to absorb light in one of the most photon-dense regions of the solar spectrum, such compounds are of great interest for application as photoactive materials in organic optoelectronics, in particular, in dye-sensitized solar cells. To achieve fine tuning of the optical and electrochemical properties, the electron-poor thiophene-bis-lactone moiety has been decorated with donor (D) and acceptor groups (A), targeting fully conjugated D–A−π–A structures. The designed structures have been investigated by means of DFT and time-dependent DFT calculations, and the most promising dyes have been synthesized. These molecules represent the very first preparation of unsymmetrical Pechmann derivatives. Optical and electrochemical properties of the new dyes have been studied by cyclic voltammetry and UV–vis and fluorescence spectroscopy. In two cases, test cells were built proving that a photocurrent can indeed be generated when using electrolytes especially formulated for narrow-band-gap dyes, although with a very low efficiency