Four new D-π-A organic dyes incorporating either a thiazolo [5,4-d]thiazole bicyclic system (TTZ1-2) or a benzo [1,2d:4,5-dЈ]bisthiazole tricyclic unit (BBZ1-2) have been synthesized and fully characterized. The key steps of the synthesis include an efficient MW-assisted preparation of the thiazolo-[5,4-d]thiazole core and selective functionalization of two different dihalothienyl derivatives through Suzuki coupling. All the compounds showed photo-and electrochemical properties compatible with their employment in dye-sensitized solar cells. In addition, their electronic structure and transitions were investigated by means of TD-DFT calculations. Dye-Eur.

We report a joint experimental and computational study into the spectroscopic properties of a prototypical D5 organic dye, both in solution and adsorbed on a TiO2 surface, with the aim of modeling and quantifying the UV/Vis spectral shifts that occur in the different explored environments. Going from the dye in solution to dye-sensitized TiO2, various factors may shift the position of the UV/Vis absorption maximum, both towards longer and shorter wavelengths. Here we have focused on the effect of dye aggregation on TiO2, surface protonation, and solvent effects. The D5 dye forms stable aggregates on the TiO2 surface that cause spectral blueshifts. We used different sensitization conditions to vary the dye loading and thus the extent of dye aggregation. For each sensitization condition, we explored protonated and native TiO2 films. Computational modeling of different dimeric aggregates with increasing intermolecular interactions and simulation of the associated optical responses also confirm the observed spectral blueshifts. Our results show that both the presence of surface protons and solvent stabilize the excited state of the adsorbed dye molecules, which causes a marked redshift in the absorption maximum and thus moves in the opposite direction to the shift due to the increase in the surface coverage.

A multinuclear NMR study shows that the deprotonation of diphenylphosphine-borane by n-BuLi in THF leads to a disolvated lithium phosphido-borane Ph(2)P(BH(3))Li of which Li(+) is connected to the hydrides on the boron and two THF molecules rather than to the phosphorus. This entity behaves as both a phosphination and a reducing agent, depending on the kinetic or thermodynamic control imposed to the reaction medium. Density functional theory computations show that H(2)P(BH(3))Li exhibits a ditopic character (the lithium cation can be in the vicinity of the hydride or of the phosphorus). It explains its dual reactivity (H- or P-addition), both routes going through somewhat similar six-membered transition states with low activation barriers.