This last century, the development of new medicinal molecules represents a real breakthrough in terms of humans and animal life expectancy and quality of life. However, this success is tainted by negative environmental consequences. Indeed, the synthesis of drug candidates requires the use of many chemicals, solvents, and processes that are very hazardous, toxic, energy consuming, expensive, and generates a large amount of waste. Many large pharmaceutical companies have thus moved to using green chemistry practices for drug discovery, development, and manufacturing. One of them is the use of energy-efficient activation techniques, such as ultrasound. This review summarizes the latest most representative works published on the use of ultrasound for sustainable bioactive molecules synthesis.

Controlling electrochemiluminescence (ECL) color(s) is crucial for many applications ranging from multiplexed bioassays to ECL microscopy. This can only be achieved through the fundamental understanding of high-energy electron-transfer processes in complex and competitive reaction schemes. Recently, this field has generated huge interest, but the effective implementation of multicolor ECL is constrained by the limited number of ECL-active organometallic dyes. Herein, the first self-enhanced organic ECL dye, a chiral red-emitting cationic diaza [4]helicene connected to a dimethylamino moiety by a short linker, is reported. This molecular system integrates bifunctional ECL features (i.e. luminophore and coreactant) and each function may be operated either separately or simultaneously. This unique level of control is enabled by integrating but decoupling both molecular functions in a single molecule. Through this dual molecular reactivity, concomitant multicolor ECL emission from red to blue with tunable intensity is readily obtained in aqueous media. This is done through competitive electron-transfer processes between the helicene and a ruthenium or iridium dye. The reported approach provides a general methodology to extend to other coreactant/luminophore systems, opening enticing perspectives for spectrally distinct detection of several analytes, and original analytical and imaging strategies.

A series of water-soluble helicene dyes generating intense electrochemiluminescence (ECL) signal in physiological conditions is reported.

Deep eutectic solvents (DESs) are of particular interest for electrometallurgy processes, since intrinsically conductive and electrochemically stable in a wide range of potentials. Cheaper and greener than conventional ionic liquids, DESs are often bio-sourced and exhibit a higher biodegradability. Ethaline, a DES composed of choline chloride (ChCl) as hydrogen bond acceptor and ethylene glycol (EG) as hydrogen bond donor in 1:2 molar proportions (Et 1:2), is commonly used in electrometallurgy thanks to its good transport properties. However, if ChCl can be considered as a “green” reactant, this is not the case for EG. A DES with a lower toxicity can be obtained by replacing EG by propylene glycol (PG), widely used in cosmetics and pharmacology, yielding a DES called Propeline. The present paper explores the potential of this lesser-known DES in the electrometallurgy of precious metals. Because changing the hydrogen bond donor leads to a modification in the DES bulk properties, the first part of this work deals with the determination of PG-based DESs’ density, viscosity, and conductivity, which are properties of interest for electrochemical processes. The influence of water and PG content is presented and values are compared to those of Ethaline. It appears that ChCl:PG in a molar ratio 1:3 (Pr 1:3) presents the best transport properties. The potentiality of this solvent for the electrometallurgy of precious metals is then discussed: electrochemical stability and electrochemical systems of Ag, Pd, and Au are compared in Pr 1:3 and Et 1:2. Finally, diffusion coefficients of the metallic species and the DES components are given, determined by electrochemical and NMR techniques, respectively.

Recycling of photovoltaic (PV) cells is a challenge for recovery of silver and copper, located in the core layer of panels. However, recovery of pure silver continues to be difficult due to parasitic reactions involving co-deposition of copper and silver. This work investigates the electrochemical behavior of Choline-chloride based eutectic mixtures (Ethaline, Propeline, Oxaline, and Reline) in order to achieve selective silver recovery in reproducible conditions. This is possible due to a stable hydration level of 5% achieved at 50 °C, where the physico-chemical and electrochemical properties were found to be stable. The nature of silver or copper complexes in eutectic mixtures was then studied to understand the electrochemical behavior of metal complexes. High-purity silver electrodeposits were obtained in two different Ag: Cu ratios of 1: 1 and 1:17, respectively, the latter mimicking the ratio obtained in PV waste leaching solutions. High silver recovery rate were obtained independently on the eutectic mixture. In the lower Ag: Cu ratio (1:17), purity of the silver deposit depends on the nature of the copper complexes and on electrolyte viscosity. In Reline, a copper-free silver deposit was obtained with a high recovery rate reaching 94.6%.