Surfactant Micellar and Vesicle Microenvironments and Structures under Synthetic Organic Conditions

Abstract

Fluorescence lifetime imaging microscopy (FLIM) reveals vesicle sizes, structures, microenvironments, reagent partitioning, and system evolution with two chemical reactions for widely used surfactant–water systems under conditions relevant to organic synthesis, including during steps of Negishi cross-coupling reactions. In contrast to previous investigations, the present experiments characterize surfactant systems with representative organohalide substrates at high concentrations (0.5 M) that are reflective of the preparative-scale organic reactions performed and reported in water. In the presence of representative organic substrates, 2-iodoethylbenzene and 2-bromo-6-methoxypyridine, micelles swell into emulsion droplets that are up to 20 μm in diameter, which is 3–4 orders of magnitude larger than previously measured in the absence of an organic substrate (5–200 nm). The partitioning of reagents in these systems is imaged through FLIMdemonstrated here with nonpolar, amphiphilic, organic, basic, and oxidative-addition reactive compounds, a reactive zinc metal powder, and a palladium catalyst. FLIM characterizes the chemical species and/or provides microenvironment information inside micelles and vesicles. These data show that surfactants cause surfactant-dictated microenvironments inside smaller micelles (<200 nm) but that addition of a representative organic substrate produces internal microenvironments dictated primarily by the substrate rather than by the surfactant, concurrent with swelling. Addition of a palladium catalyst causes the internal environments to differ between vesiclesinformation that is not available through nor predicted from prior analytical techniques. Together, these data provide immediately actionable information for revising reaction models of surfactant–water systems that underpin the development of sustainable organic chemistry in water.

Decoupling of the Confused Complex in Oxidation of 3,3′,5,5′-Tetramethylbenzidine for the Reliable Chromogenic Bioassay

“…These results further confirmed that the addition of TMB caused morphological changes in the micelles. It was mainly due to the hydrophobic interaction that drives TMB into the hydrophobic cavity of SDS micelles. , Moreover, from a kinetic point of view, such a confined space would improve the local concentration of reactants and accelerate the oxidation reaction rate, i.e., making TMB be in an “activated” state. To confirm this assumption, the TMB oxidation in aqueous solution with and without SDS micelles was explored under light irradiation that would photochemically produce a trace amount of free ROS.…”

“…In stage II (from 400 to 1200 s), a gradual decrease in the scattering intensity was observed, indicating the oxidation of TMB and the departure of the oxidation product from the SDS micelles. Due to the positive electrical and hydrophilic nature of the oxidation products, the oxidation products would move to the outer surface of the micelles that was hydrophobic and negatively charged properties . To verify this assumption, the ζ-potential of the mixed solution of SDS micelles (10 mM) and TMB (0.05 mM) was determined to be −61.55 ± 1.14 mV, while the ζ-potential of the solution changed to −37.43 ± 1.65 mV after the addition of H 2 O 2 (100 mM).…”

“…Due to the positive electrical and hydrophilic nature of the oxidation products, 44 the oxidation products would move to the outer surface of the micelles that was hydrophobic and negatively charged properties. 40 To verify this assumption, the ζ-potential of the mixed solution of SDS micelles (10 mM) and TMB (0.05 mM) was determined to be −61.55 ± 1.14 mV, while the ζ-potential of the solution changed to −37.43 ± 1.65 mV after the addition of H 2 O 2 (100 mM). The decrease of the negative ζ-potential supported the absorption of positive two-electron TMB oxidation product on the outer surface of SDS micelles.…”

Core-Labeled Reverse Micelle-Based Supramolecular Solvents for Assisted Quick and Sensitive Determination of Amitriptyline in Wastewater

“…As part of sustainability, contemporary analytical chemistry has developed miniaturized and eco-friendly analytical methods employing biodegradable and green solvents . Unique microenvironments provided by surfactant micellar structures − have been explored in green organic synthesis, for the development of nanostructured hydrogel materials, for developing micelles with responsive emission, FRET-enabled micelles for nucleic acid detection, and even to attain aqueous sensing of biorelevant anions . Similarly, the tailored supramolecular solvent (SUPRAS) is stepping sustainability ahead and these solvents find application in separation techniques, such as liquid–liquid extraction and chromatography, due to their ability to selectively solvate desired molecules .…”

Implementation of micelle-enabled C(sp2)–C(sp3) cross-electrophile coupling in pharmaceutical synthesis

“…12 In addition, such chemistry tends to happen with reprotoxic polar aprotic solvents, such as DMA, DMF or NMP, 13 which are not preferred due to the tedious purification processes they necessitate, on top of their now well-recognized sustainability drawbacks. 14 Meanwhile, chemistry-in-water technology has become more and more popular owing to the demand of reducing the environmental footprint, 15 as one example demonstrated by Lipshutz and co-workers in 2009, who reported a palladium-catalyzed aryl–alkyl cross coupling under micellar conditions. 16…”