In this review, we highlight the use of organic photoredox catalysts in a myriad of synthetic transformations with a range of applications. This overview is arranged by catalyst class where the photophysics and electrochemical characteristics of each is discussed to underscore the differences and advantages to each type of single electron redox agent. We highlight both net reductive and oxidative as well as redox neutral transformations that can be accomplished using purely organic photoredox-active catalysts. An overview of the basic photophysics and electron transfer theory is presented in order to provide a comprehensive guide for employing this class of catalysts in photoredox manifolds.

Organic Photoredox Catalysis

3.6.1. Polishing and Cleaning 2663 3.6.2. Vacuum and Heat Treatments 2664 3.6.3. Carbon Electrode Activation 2665 3.7. Summary and Generalizations 2666 4. Advanced Carbon Electrode Materials 2666 4.1. Microfabricated Carbon Thin Films 2666 4.2. Boron-Doped Diamond for Electrochemistry 2668 4.3. Fibers and Nanotubes 2669 4.4. Carbon Composite Electrodes 2674 5. Carbon Surface Modification 2675 5.1. Diazonium Ion Reduction 2675 5.2. Thermal and Photochemical Modifications 2679 5.3. Amine and Carboxylate Oxidation 2680 5.4. Modification by “Click” Chemistry 2681 6. Synopsis and Outlook 2681 7. Acknowledgments 2682 8. References 2682

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Advanced carbon electrode materials for molecular electrochemistry.

Electrochemistry represents one of the most intimate ways of interacting with molecules. This review discusses advances in synthetic organic electrochemistry since 2000. Enabling methods and synthetic applications are analyzed alongside innate advantages as well as future challenges of electroorganic chemistry.

Synthetic Organic Electrochemical Methods Since 2000: On the Verge of a Renaissance

Compounds Currently in Phase II−III Clinical Trials of Major Pharmaceutical Companies: New Structural Trends and Therapeutic Areas Yu Zhou,† Jiang Wang,† Zhanni Gu,† Shuni Wang,† Wei Zhu,† Jose ́ Luis Aceña,*,‡,§ Vadim A. Soloshonok,*,‡,∥ Kunisuke Izawa,* and Hong Liu*,† †Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China ‡Department of Organic Chemistry I, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel Lardizab́al 3, 20018 San Sebastiań, Spain Department of Organic Chemistry, Autońoma University of Madrid, Cantoblanco, 28049 Madrid, Spain IKERBASQUE, Basque Foundation for Science, María Díaz de Haro 3, 48013 Bilbao, Spain Hamari Chemicals Ltd., 1-4-29 Kunijima, Higashi-Yodogawa-ku, Osaka, Japan 533-0024

Next Generation of Fluorine-Containing Pharmaceuticals, Compounds Currently in Phase II–III Clinical Trials of Major Pharmaceutical Companies: New Structural Trends and Therapeutic Areas

Carbon dioxide exits in the atmosphere and is produced by the combustion of fossil fuels, the fermentation of sugars and the respiration of all living organisms. An active goal in organic synthesis is to take this carbon--trapped in a waste product--and re-use it to build useful chemicals. Recent advances in organometallic chemistry and catalysis provide effective means for the chemical transformation of CO₂ and its incorporation into synthetic organic molecules under mild conditions. Such a use of carbon dioxide as a renewable one-carbon (C1) building block in organic synthesis could contribute to a more sustainable use of resources.

/pdf/using-carbon-dioxide-as-a-building-block-in-organic-4s0h674ulv.pdf

Using carbon dioxide as a building block in organic synthesis

Carbon dioxide is ubiquitous and a vital molecule for maintaining life on our planet. However, the ever-increasing emission of anthropogenic CO2 into our atmosphere has provoked dramatic climate changes. In principle, CO2 could represent an important one-carbon building block for the chemical industry, yet its high thermodynamic and kinetic stability has limited its applicability to only a handful of industrial applications. On the other hand, carbon monoxide represents a more versatile reagent applied in many industrial transformations. Here we review the different methods for converting CO2 to CO with specific focus on the reverse water gas shift reaction, main element reductants, and electrochemical protocols applying homogeneous and heterogeneous catalysts. Particular emphasis is given to synthetic methods that couple the deoxygenation step with a follow-up carbonylation step for the synthesis of carbonyl-containing molecules, thus avoiding the need to handle or store this toxic but highly synthetically useful diatomic gas. CO is a vital building block in organic synthesis but, due to its toxicity, storage and transport can be problematic. This review focuses on the methods — both chemical and electrochemical — for the in situ generation of CO from CO2, and its subsequent incorporation into chemicals through catalytic means.

Chemically and electrochemically catalysed conversion of CO 2 to CO with follow-up utilization to value-added chemicals

In a comparative study of the electrocatalytic CO2 reduction, cobalt meso-tetraphenylporphyrin (CoTPP) is used as a model molecular catalyst under both homogeneous and heterogeneous conditions. In the former case, employing N,N-dimethylformamide as solvent, CoTPP performs poorly as an electrocatalyst giving low product selectivity in a slow reaction at a high overpotential. However, upon straightforward immobilization of CoTPP onto carbon nanotubes, a remarkable enhancement of the electrocatalytic abilities is seen with CO2 becoming selectively reduced to CO (>90 %) at a low overpotential in aqueous medium. This effect is ascribed to the particular environment created by the aqueous medium at the catalytic site of the immobilized catalyst that facilitates the adsorption and further reaction of CO2. This work highlights the significance of assessing an immobilized molecular catalyst from more than homogeneous measurements alone.

Enhanced Catalytic Activity of Cobalt Porphyrin in CO2 Electroreduction upon Immobilization on Carbon Materials

Earth-abundant transition metal (Fe, Co, or Ni) and nitrogen-doped porous carbon electrocatalysts (M-N-C, where M denotes the metal) were synthesized from cheap precursors via silica-templated pyrolysis. The effect of the material composition and structure (i.e., porosity, nitrogen doping, metal identity, and oxygen functionalization) on the activity for the electrochemical CO2 reduction reaction (CO2RR) was investigated. The metal-free N-C exhibits a high selectivity but low activity for CO2RR. Incorporation of the Fe and Ni, but not Co, sites in the N-C material is able to significantly enhance the activity. The general selectivity order for CO2-to-CO conversion in water is found to be Ni > Fe ≫ Co with respect to the metal in M-N-C, while the activity follows Ni, Fe ≫ Co. Notably, the Ni-doped carbon exhibits a high selectivity with a faradaic efficiency of 93% for CO production. Tafel analysis shows a change of the rate-determining step as the metal overtakes the role of the nitrogen as the most activ...

Selective CO2 Reduction to CO in Water using Earth-Abundant Metal and Nitrogen-Doped Carbon Electrocatalysts

The development of efficient and selective luminescent probes for reactive oxygen species, particularly for singlet molecular oxygen, is currently of great importance. In this study, the photochemical behavior of Singlet Oxygen Sensor Green(®) (SOSG), a commercially available fluorescent probe for singlet oxygen, was examined. Despite published claims to the contrary, the data presented herein indicate that SOSG can, in fact, be incorporated into a living mammalian cell. However, for a number of reasons, caution must be exercised when using SOSG. First, it is shown that the immediate product of the reaction between SOSG and singlet oxygen is, itself, an efficient singlet oxygen photosensitizer. Second, SOSG appears to efficiently bind to proteins which, in turn, can influence uptake by a cell as well as behavior in the cell. As such, incorrect use of SOSG can yield misleading data on yields of photosensitized singlet oxygen production, and can also lead to photooxygenation-dependent adverse effects in the system being investigated.

Kim Daasbjerg

Papers

Chemically and electrochemically catalysed conversion of CO 2 to CO with follow-up utilization to value-added chemicals

Enhanced Catalytic Activity of Cobalt Porphyrin in CO2 Electroreduction upon Immobilization on Carbon Materials

Selective CO2 Reduction to CO in Water using Earth-Abundant Metal and Nitrogen-Doped Carbon Electrocatalysts

Singlet Oxygen Sensor Green®: photochemical behavior in solution and in a mammalian cell.

Anodic Oxidation and Organocatalysis: Direct Regio‐ and Stereoselective Access to meta‐Substituted Anilines by α‐Arylation of Aldehydes