Versatile Tools for Understanding Electrosynthetic Mechanisms

Electrosynthesis is a popular, green alternative to traditional organic methods. Understanding the mechanisms is not trivial yet is necessary to optimize reaction processes. To this end, a multitude of analytical tools is available to identify and quantitate reaction products and intermediates. The first portion of this review serves as a guide that underscores electrosynthesis fundamentals, including instrumentation, electrode selection, impacts of electrolyte and solvent, cell configuration, and methods of electrosynthesis. Next, the broad base of analytical techniques that aid in mechanism elucidation are covered in detail. These methods are divided into electrochemical, spectroscopic, chromatographic, microscopic, and computational. Technique selection is dependent on predicted reaction pathways and electrogenerated intermediates. Often, a combination of techniques must be utilized to ensure accuracy of the proposed model. To conclude, future prospects that aim to enhance the field are discussed.

No photocatalyst required--versatile, visible light mediated transformations with polyhalomethanes

A visible light mediated, but photocatalyst-free method for the oxidative α-CH functionalization of tertiary amines with a broad scope of carbon- and heteroatom nucleophiles using polyhalomethanes has been developed. In addition, the pivotal visible light triggered activation of polyhalomethanes offers mild conditions for efficient Kharasch-type additions onto non-activated olefins. Preliminary mechanistic studies are reported.

Bridge- and solvent-mediated intramolecular electronic communications in ubiquinone-based biomolecular wires

Intramolecular electronic communications of molecular wires play a crucial role for developing molecular devices. In the present work, we describe different degrees of intramolecular electronic communications in the redox processes of three ubiquinone-based biomolecular wires (Bis-CoQ₀s) evaluated by electrochemistry and Density Functional Theory (DFT) methods in different solvents. We found that the bridges linkers have a significant effect on the electronic communications between the two peripheral ubiquinone moieties and solvents effects are limited and mostly depend on the nature of solvents. The DFT calculations for the first time indicate the intensity of the electronic communications during the redox processes rely on the molecular orbital elements V_L for electron transfer (half of the energy splitting of the LUMO and LUMO+1), which is could be affected by the bridges linkers. The DFT calculations also demonstrates the effect of solvents on the latter two-electron transfer of Bis-CoQ₀s is more significant than the former two electrons transfer as the observed electrochemical behaviors of three Bis-CoQ₀s. In addition, the electrochemistry and theoretical calculations reveal the intramolecular electronic communications vary in the four-electron redox processes of three Bis-CoQ₀s.

Computational electrochemistry: prediction of liquid-phase reduction potentials

This article reviews recent developments and applications in the area of computational electrochemistry. Our focus is on predicting the reduction potentials of electron transfer and other electrochemical reactions and half-reactions in both aqueous and nonaqueous solutions. Topics covered include various computational protocols that combine quantum mechanical electronic structure methods (such as density functional theory) with implicit-solvent models, explicit-solvent protocols that employ Monte Carlo or molecular dynamics simulations (for example, Car-Parrinello molecular dynamics using the grand canonical ensemble formalism), and the Marcus theory of electronic charge transfer. We also review computational approaches based on empirical relationships between molecular and electronic structure and electron transfer reactivity. The scope of the implicit-solvent protocols is emphasized, and the present status of the theory and future directions are outlined.

A new generation of cysteine derivatives with three active antioxidant centers: improving reactivity and stability

The development of new antioxidants with enhanced activity constitutes a very active research field as it can contribute to the improvement of human health. Although the antioxidant activity occurs through different mechanisms, usually most of the antioxidant molecules present a unique active center which is able to react following a specific way. To overcome this weakness and in the belief that the coupling of different antioxidant groups is a good strategy to obtain multipotent antioxidants, the effect of introducing different N-protective groups on the cysteine core is evaluated by using DFT. As a result, in this work we present a multicenter antioxidant, N-(9-fluorenylmethyloxycarbonyl)cysteine methyl ester 8, able to fight efficiently through different mechanisms against free radicals independently of their nature. This antioxidant appears to be the first one of a promising new class of multipotent antioxidants with three operative centers: C(α) that is a good hydrogen donor, the Fmoc group that is a good electron donor and the all-around thiol group. Besides, its neutral radical shows a high stability due to the captodative effect in such a way that the subsequent toxic effects would be avoided. Then, its experimental radical-trapping antioxidant activity postulates compound 8 as a prototype of antioxidants more versatile and efficient than N-acetylcysteine, ascorbic acid or Trolox.