Development of the P-Arylation of Dithieno[3,2-b : 2',3'-d]phosphole with Aryl Iodonium Salts.

P-Arylation of dithieno[3,2-b : 2',3'-d]phosphole toward cationic phenyl phospholium species using diaryliodonium reagents was explored. Multiple conditions were tested to optimize the reaction, including variation of solvent, temperature, stoichiometry, time, and aryliodonium species employed. Initial use of diphenyliodonium chloride led to an unexpected dithienophosphole Cu(I) chloride complex that was characterized crystallographically. Alternatively, the use of diphenyliodonium hexafluorophosphate in ethanol under microwave conditions led to the successful isolation of the P-arylated target. The phenyl dithienophospholium species exhibits blue luminescence with a quantum yield of 100 % in solution that is considerably red-shifted in the solid state. The photophysics and solid-state organization of the new species were compared with those of a related methyl congener, showing distinct differences that are assigned to the nature of the carbon-based substituent at the phosphorus center, which was also confirmed by DFT calculations, and the supramolecular organization in the solid state.

Not So Innocent After All: Interfacial Chemistry Determines Charge-Transport Efficiency in Single-Molecule Junctions.

Most studies in molecular electronics focus on altering the molecular wire backbone to tune the electrical properties of the whole junction. However, it is often overlooked that the chemical structure of the groups anchoring the molecule to the metallic electrodes influences the electronic structure of the whole system and, therefore, its conductance. We synthesised electron-accepting dithienophosphole oxide derivatives and fabricated their single-molecule junctions. We found that the anchor group has a dramatic effect on charge-transport efficiency: in our case, electron-deficient 4-pyridyl contacts suppress conductance, while electron-rich 4-thioanisole termini promote efficient transport. Our calculations show that this is due to minute changes in charge distribution, probed at the electrode interface. Our findings provide a framework for efficient molecular junction design, especially valuable for compounds with strong electron withdrawing/donating backbones.