Arylation in the 4- and 7-positions of 2,1,3-benzothiadiazole (BT) and its monofluoro- (MFBT) and difluoro- (DFBT) derivatives by (hetero)aryl bromides using Pd-catalyzed C–H activation has been investigated. MFBT and DFBT can be diarylated in moderate to high yields (up to 96% for DFBT) by a variety of aryl bromides. DFBT can be sequentially arylated using two different aryl bromides to give differentially substituted DFBT derivatives. The moderate to high yields of doubly arylated MFBT and DFBT and the ability to obtain differentially substituted products can be applied to a variety of organic photonic and electronic materials.

Macrocyclic peptides are important therapeutic candidates due to their improved physicochemical properties in comparison to their linear counterparts.

We report the use of a sulfonated biarylphosphine ligand (sSPhos) to promote the chemoselective modification of cysteine containing proteins and peptides with palladium reagents in aqueous medium. The use of sSPhos allowed for the isolation of several air-stable and water-soluble mono- and bis-palladium reagents, which were used in an improved protocol for the rapid S-arylation of cysteines under benign and physiologically relevant conditions. The cosolvent-free aqueous conditions were applied to the conjugation of a variety of biomolecules with affinity tags, heterocycles, fluorophores, and functional handles. Additionally, bis-palladium reagents were used to perform macrocyclization of peptides bearing two cysteine residues.

Three D−A−π−A organic dyes based on 5,6difluoro-2,1,3-benzothiadiazole (DFBTD) were synthesized by sequential direct arylation and characterized by spectroscopic and electrochemical techniques. Compared to 2,1,3-benzothiadiazole (BTD) analogue, the presence of two fluorine atoms on DFBTD results not only in a significant increase in the molar absorptivity but also in a blue shift of the onset of the absorption spectra. In the system of DFBTD-based sensitizers, replacing the thienyl unit bridge with disubstituted cyclopenta[1,2-b:5,4-b′]dithiophene (CPDT) further increases molar absorptivity and decreases the oxidation potential of the excited state E (s+/s*) . Similarly, changing the indoline donor to 4-butoxy-N-(4-butoxyphenyl)-N-phenylaniline increases the optical band gap and decreases the oxidation potential of the excited state E (s+/s*) of the sensitizer. The correlation between the molecular structure of these sensitizers and the photovoltaic performance of the dye cells were examined using current− voltage scan, incident photon to electron conversion efficiency (IPCE), femtosecond transient absorption spectroscopy (TAS), and electrochemical impedance spectroscopy (EIS). The observed change of the photovoltage and photocurrent upon changing the molecular structure of the sensitizers are discussed in terms of the charge injection from the excited state to the interband gap states of TiO 2 and the charge recombination between injected electrons into TiO 2 film and electrolyte. In all, it is found that the most efficient D−A−π−A dye achieved an open circuit voltage of 0.717 V, short circuit current density of 18.8 mA/cm 2 , corresponding to an overall power conversion efficiency of 9.1%.