Submerging a Biomimetic Metallo‐Receptor in Water for Molecular Recognition: Micellar Incorporation or Water Solubilization? A Case Study

Specific Binding of Primary Ammoniums in Aqueous Media by Homooxacalixarenes Incorporated into Micelles

The development of artificial receptors for efficient recognition of analytes in water is a challenging task. Homooxacalix[3]arene-based receptor 1, which is selective toward primary ammoniums in organic solvents, was transferred into water following two different strategies: direct solubilization and micellar incorporation. Extensive ¹H NMR studies showed that recognition of ammoniums is only observed in the case of micellar incorporation, highlighting the beneficial effect of the microenvironment of the micellar core. The selectivity of the system for primary ammoniums over secondary and tertiary ones was also maintained. The hydrophobic effect plays an important role in the recognition properties, which are counterion-dependent due to the energy penalty for the dissociation of certain ammonium salts in the apolar micellar core. This study shows that the straightforward self-assembly process used for the encapsulation of artificial receptors in micelles is an efficient strategy for developing water-soluble nanosized supramolecular recognition systems.

Impact of positive charge and ring-size on interactions of calixarenes with DNA, RNA and nucleotides

Comparison of various calix[6]arene and calix[4]arene derivatives revealed that only analogues bearing permanent positive charge non-covalently bind to ds-DNA and ds-RNA, by insertion into DNA minor groove or RNA major...

Hetero-Tetranuclear Cu2+ /Ca2+ /Ca2+ /Cu2+ Architectures Based On Malten Ligand: Scaffold for Anion Binding

The hetero-tetranuclear Cu²⁺ /Ca²⁺ /Ca²⁺ /Cu²⁺ complex obtained with the N,N'-bis((3-hydroxy-4-pyron-2-yl)methyl)-N,N'-dimethylethylendiamine (Malten) ligand has been studied in solid and solution states as scaffold to bind anions. Three crystal structures showing the same metal ions sequence have been examined; they display a tetracharged complex cation neutralized by four monocharged anions. The anions play two different roles: as coordinated (two ClO₄ ^- , Cl^- or NO₃ ^- ) or ancillary (two ClO₄ ^- ) guests. The tetranuclear scaffold hosts two anions also in aqueous and ethanol solutions. Spectrophotometric studies in ethanol allowed to determine the addition constant values for Cl^- and Br^- (Log K_1-2 =4.43(4), 4.39(3) for Cl^- , 3.80(3), 3.54(2) for Br^- ) while the others, although bound, showed lower affinity for the scaffold. Both the crystals and the solutions change their color depending on the added anion, namely pink, dark green or blue in the presence of ClO₄ ^- , Cl^- or NO₃ ^- , respectively, thus the presence of the different anions is visible to the naked eye. The hetero-tetranuclear Cu²⁺ /Ca²⁺ /Ca²⁺ /Cu²⁺ complex is a versatile architecture to be used as scaffold for anion binding.

Halide Photoredox Chemistry

Halide photoredox chemistry is of both practical and fundamental interest. Practical applications have largely focused on solar energy conversion with hydrogen gas, through HX splitting, and electrical power generation, in regenerative photoelectrochemical and photovoltaic cells. On a more fundamental level, halide photoredox chemistry provides a unique means to generate and characterize one electron transfer chemistry that is intimately coupled with X-X bond-breaking and -forming reactivity. This review aims to deliver a background on the solution chemistry of I, Br, and Cl that enables readers to understand and utilize the most recent advances in halide photoredox chemistry research. These include reactions initiated through outer-sphere, halide-to-metal, and metal-to-ligand charge-transfer excited states. Kosower's salt, 1-methylpyridinium iodide, provides an early outer-sphere charge-transfer excited state that reports on solvent polarity. A plethora of new inner-sphere complexes based on transition and main group metal halide complexes that show promise for HX splitting are described. Long-lived charge-transfer excited states that undergo redox reactions with one or more halogen species are detailed. The review concludes with some key goals for future research that promise to direct the field of halide photoredox chemistry to even greater heights.

A biomimetic strategy for the selective recognition of organophosphates in 100% water: synergies of electrostatic interactions, cavity embedment and metal coordination

A biomimetic receptor allows selective recognition of organophosphates in water thanks to multipoint recognition associating coordination, electrostatics and cavity hosting.