Near-infrared electrochemiluminescence in water through regioselective sulfonation of diaza [4] and [6]helicene dyes.

A series of water-soluble helicene dyes generating intense electrochemiluminescence (ECL) signal in physiological conditions is reported. Those species were prepared using diaza [4] and [6]helicenes as structural cores modified with sulfonate groups in various positions. Such groups improve their water solubility and can induce a red-shifted emission. Efficient ECL up to the near-infrared is achieved in water, demonstrating a viable strategy for the design of new near-infrared ECL dyes for bioassays and microscopy.

Ultrasound for Drug Synthesis: A Green Approach.

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.

Self-enhanced multicolor electrochemiluminescence by competitive electron-transfer processes.

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.

Merging polyacenes and cationic helicenes: from weak to intense chiroptical properties in the far red region.

A series of helical tetracenes and pentacenes was synthesized from cationic [6] and [4]helicene precursors. These colorful acenes fluoresce in the far red region. While [4]helicene-based pentacenes exhibit chiroptical properties mainly in the UV region, [6]helicene-derived tetracenes show enhanced ECD in the visible range, in addition to clear CPL responses. This difference is rationalized using first principles.

Synthesis and Identification of Aryl and Alkyl Gem-Dilithium Phosphido-Boranes: A Boost to the Chemistry of Phosphandiides.

The synthesis and identification of unprecedented gem-dianionic phosphorus compounds, that is, gem-dilithium phosphido-boranes Li2 [RP⋅BH3 ], with R=Ph or Cy, are reported in THF solution. These were obtained by double deprotonation of the corresponding primary phosphine-borane precursors RPH2 ⋅BH3 . Their in-depth structural study, based on multinuclear (1 H, 6 Li, 7 Li, 11 B, 13 C, 31 P) mono- and bi-dimensional NMR analyses, indicates a strong influence of the phosphorus substituent on the structure of the gem-dianionic phosphorus structure; a monomeric arrangement was obtained when R=phenyl, whereas a cyclic oligomer was observed for R=cyclohexyl. These compounds represent a new type of useful reagent, and their access paves the way for the concept of "RP synthons" (i.e., RP2- phosphandiides), likely to be the most flexible precursors of a variety of phosphorus targets.

Specific labeling of mitochondria of Chlamydomonas with cationic helicene fluorophores.

Twelve cationic helicenes and one triangulene were tested for the specific labeling of mitochondria from algal cells. Octyl ester derivative 5 readily penetrates algal cells and gives rise to clear fluorescence patterns when it is used at concentrations in the µM range. Under these conditions, cell structures are well preserved and cell survival is not compromised. Cationic helicene compounds such as 5 provide new useful tools for examining the mitochondrial network and its dynamics including fission and fusion events.

Enantiospecific Elongation of Cationic Helicenes by Electrophilic Functionalization at Terminal Ends.

A strategy for late-stage electrophilic functionalizations of cationic helicenes is exposed. Thanks to strongly acidic conditions that permit reversible electrophilic substitutions, regioselective acylations, sulfonylations, or alkylations occur at the extremity(ies) of the helical cores. Extended [5] or [6]helicenes can then be generated from cationic [4]helicenes in successive one-pot elongation processes. Retention of configuration and excellent enantiospecificity (up to 99 %) are observed for the helicene growth in the enantiopure series.

A Lithium Amide Protected Against Protonation in the Gas Phase: Unexpected Effect of LiCl.

In cold THF and in the presence of LiCl, a lithium pyrrolidinylamide forms a 1:1 mixed aggregate, which is observed directly by ESI-MS. Gas-phase protonation of this species leads to selective transfer of H(+) to the chlorine, suggesting that LiCl shields the amide nitrogen and prevents its direct protonation.