Anthradithiophene (ADT)-Based Polymerized Non-Fullerene Acceptors for All-Polymer Solar Cells

Realizing efficient all-polymer solar cell (APSC) acceptors typically involves increased building block synthetic complexity, hence potentially unscalable syntheses and/or prohibitive costs. Here we report the synthesis, characterization, and implementation in APSCs of three new polymer acceptors P1-P3 using a scalable donor fragment, bis(2-octyldodecyl)anthra[1,2-b : 5,6-b']dithiophene-4,10-dicarboxylate (ADT) co-polymerized with the high-efficiency acceptor units, NDI, Y6, and IDIC. All three copolymers have comparable photophysics to known polymers; however, APSCs fabricated by blending P1, P2 and P3 with donor polymers PM5 and PM6 exhibit modest power conversion efficiencies (PCEs), with the champion P2-based APSC achieving PCE=5.64 %. Detailed morphological and microstructural analysis by AFM and GIWAXS reveal a non-optimal APSC active layer morphology, which suppresses charge transport. Despite the modest efficiencies, these APSCs demonstrate the feasibility of using ADT as a scalable and inexpensive electron rich/donor building block for APSCs.

Green Synthesis of Pd Nanoparticles for Sustainable and Environmentally Benign Processes

Among transition metal nanoparticles, palladium nanoparticles (PdNPs) are recognized for their high catalytic activity in a wide range of organic transformations that are of academic and industrial importance. The increased interest in environmental issues has led to the development of various green approaches for the preparation of efficient, low-cost and environmentally sustainable Pd-nanocatalysts. Environmentally friendly solvents, non-toxic reducing reagents, biodegradable capping and stabilizing agents and energy-efficient synthetic methods are the main aspects that have been taken into account for the production of Pd nanoparticles in a green approach. This review provides an overview of the fundamental approaches used for the green synthesis of PdNPs and their catalytic application in sustainable processes as cross-coupling reactions and reductions with particular attention afforded to the recovery and reuse of the palladium nanocatalyst, from 2015 to the present.

Polarclean/Water as a Safe and Recoverable Medium for Selective C2-Arylation of Indoles Catalyzed by Pd/C

Herein, we report the use of nontoxic, water-miscible Polarclean as a safe dipolar aprotic solvent for the metal-catalyzed direct C2-H arylation of indoles using Pd/C as a catalyst. The developed method allows reaching excellent yields and regioselectivities, and it tolerates various substituents on both indole and diaryliodonium salt scaffolds. Polarclean is fully recoverable and reusable; it shows a very low leaching of the metal catalyst, allowing its complete recovery and reuse for at least six representative reaction runs.

Optimized Immobilization Strategy for Dirhodium(II) Carboxylate Catalysts for C-H Functionalization and Their Implementation in a Packed Bed Flow Reactor

Herein we demonstrate a packed bed flow reactor capable of achieving highly regio- and stereoselective C-H functionalization reactions using a newly developed Rh₂ (S-2-Cl-5-CF₃ TPCP)₄ catalyst. To optimize the immobilized dirhodium catalyst employed in the flow reactor, we systematically study both (i) the effects of ligand immobilization position, demonstrating the critical factor that the catalyst-support attachment location can have on the catalyst performance, and (ii) silica support mesopore length, demonstrating that decreasing diffusional limitations leads to increased accessibility of the active site and higher catalyst turnover frequency. We employ the immobilized dirhodium catalyst in a simple packed bed flow reactor achieving comparable yields and levels of enantioselectivity to the homogeneous catalyst employed in batch and maintain this performance over ten catalyst recycles.

Polarclean as a Sustainable Reaction Medium for the Waste Minimized Synthesis of Heterocyclic Compounds

Herein we report the use of Rhodiasolv^© Polarclean as a novel polar aprotic solvent for the synthesis of decorated heterocycles via dipolar cycloaddition (isooxazoles) or intramolecular C–H functionalization processes (benzo-fused chromenes). The use of Polarclean allowed to isolate the final products in good yields by simple solid filtration or liquid-liquid phase separation, avoiding the need for chromatographic purification. Moreover, since in the synthesis of benzo-fused chromenes, the metal catalyst is retained in Polarclean, the catalyst/reaction medium can be easily reused for consecutive reaction runs, without any apparent loss in efficiency. This methodology is associated with a limited waste production. These results extend the applicability of Polarclean as a promising reaction medium for the replacement of toxic petrol-based solvent.

C-H functionalization reactions under flow conditions

C-H functionalization technologies have progressed enormously in the last decade as testified by the great number of publications that have appeared in the literature, which are receiving great attention from researchers from different areas of expertise. While most of the protocols reported realize the C-H functionalization processes under batch conditions, there is a growing interest in the development of continuous-flow procedures aiming at increasing the performances of established methodologies or the definition of otherwise unfeasible transformations. This review summarizes the application of flow technologies for the realization of C-H functionalization reactions. According to the type of flow reactors necessary, two main general approaches are possible for the application of flow techniques, namely the use of homogeneous or heterogeneous conditions. Each example is discussed and accompanied by the description of the main features and benefits of the use of flow compared to batch conditions.

Avoiding hot-spots in Microwave-assisted Pd/C catalysed reactions by using the biomass derived solvent γ-Valerolactone

Herein, we report the use of γ-valerolactone as a new biomass-derived reaction medium for microwave assisted organic synthesis. The interaction of this solvent with microwaves and its heating profile under microwave irradiation has been fully characterized for the first time, demonstrating its stability and the applicability in microwave assisted Pd/C catalysed reactions avoiding the arcing phenomena frequently observed in these conditions. The use of γ-valerolactone demonstrated to be compatible with aliphatic and aromatic amines in the hydrogen transfer Pd/C mediated synthesis of benzimidazoles.