Surfactant Semiconductors as Trojan Horses in Cell-Membranes for On-Demand and Spatial Regulation of Oxidative Stress

Oxidative stress is a cause for numerous diseases and aging processes. Thus, researchers are keen to tune the level of intracellular stress and to learn from that. An unusual approach is presented here. The methodology involves multifunctional surfactants. Although their molecular design is nonbiological—a fullerenol head group attached covalently to pi-conjugated dyes—the surfactants possess superior biocompatibility. Using an intrinsic fluorescence signal as a probe, it is shown that the amphiphiles become incorporated into the Caco-2 cells. There, they are able to exhibit additional functions. The compound reduces cellular stress in dark reaction pathways. The antagonistic property is activated under irradiation, the photocatalytic production of reactive oxygen species (ROS), resulting in cell damage. The feature is activated even by near-infrared light (NIR-light) via a two-photon process. The properties as molecular semiconductors lead to a trojan horse situation and allows the programming of the spatial distribution of cytotoxicity

Hybrid Surfactants with Fullerene as Functional Unit

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Easy, efficient and versatile one-pot synthesis of Janus-type-substituted fullerenols

An efficient one-pot synthesis for Janus-type fullerenol derivatives and how to characterize them is reported. This synthesis provides access to asymmetrically substituted fullerenol with five substituents on one pole of the fullerene and polyhydroxylation moieties, mostly ether and hydroxy groups, on the rest of the fullerene core. As substituents a broad variety of primary amines can be used to obtain Janus-type amphiphilic fullerenols in good to excellent yield. These fullerenol amphiphiles can serve as suitable precursors for further reactions resulting in new applications for fullerenols.publishe

Molecular Semiconductor Surfactants with Fullerenol Head and Colored Tails for Photoconversion of Carbon Dioxide

The leaf is paramount for a material converting waste (CO2) to value with maximum sustainability. As the most important constituent, it contains the coupled photosystems II and I imbedded in the cellular membrane of chloroplasts. Can key functions of the leaf be packed in soap? We present next generation surfactants, which self-assemble to bilayer vesicles (similar to the cellular membrane), are able to absorb photons of two different VIS-wavelengths and exchange excited charge carriers (similar to the photosystems), followed by conversion of CO2 (in analogy to the leaf). The amphiphiles contain five dye molecules as the hydrophobic entity attached exclusively to one hemisphere of a polyhydroxylated fullerene (Janus-type). The manuscript reports surfactant, optical, electronic and catalytic properties. Photons adsorbed by the dyes become transferred to the fullerenol head, where they are able react with different species like with CO2 to formic acid.publishe

Molekulare Halbleiter‐Tenside mit Fullerenol‐Kopfgruppe und Farbstoffketten für die photokatalytische Umwandlung von Kohlenstoffdioxid

Das natürliche Blatt ist ein Paradebeispiel für ein System, das kontinuierlich Wertschöpfung betreibt, indem es z. B. CO2 in Zucker umwandelt. Wichtigster Bestandteil sind die gekoppelten Photosysteme II und I, die in der Zellmembran eingebettet sind. Können ihre Schlüsselfunktionen auf ein Tensid übertragen werden? Wir stellen moderne Tenside vor, die sich zu zweischichtigen Vesikeln anordnen (ähnlich der Zellmembran), fähig sind, Photonen verschiedener Wellenlängen zu absorbieren und angeregte Ladungsträger auszutauschen (ähnlich zu Photosystem II und I), sowie CO2 umzuwandeln (analog zum Blatt). Die Tenside bestehen aus fünf Farbstoffeinheiten als hydrophobe Gruppe, allesamt auf einer Seite des polyhydroxylierten Fullerenols, das als Kopfgruppe dient (Janus‐artig). Wir berichten über tensidische, optische, elektronische und katalytische Eigenschaften, sowie davon, wie von den Farbstoffen absorbierte Photonen zur Fullerenol‐Kopfgruppe transportiert werden, wo sie z. B. mit CO2 reagieren und dieses zu Ameisensäure reduzieren können.publishe

Aggregation-Induced Improvement of Catalytic Activity of Metalfullerene-Based Surfactants Used in Water Splitting Reaction

An inherent paradigm of molecular compounds used in homogeneous catalysis is that maximum performance requires maximum dispersion, and that any form of aggregation results in a loss of activity. We here present a new concept based on surfactants with functional heads, which become better catalysts when they aggregate. The head group of the surfactants is composed of a diethylenetriamine-functionalized fullerene, which coordinates Co II ions. This system is applied as an electrocatalyst for the water-splitting reaction. Detailed electrochemistry studies were performed at concentrations below and above the critical aggregation concentration (cac), when 150 nm sized vesicles are formed. While isolated surfactant molecules represent only moderately active catalysts, drastic improvement in the hydrogen evolution (HER) as well as in the oxygen evolution reactions (OER) were detected for the vesicular structures. Self-organization of the surfactants leads to an increase in turnover frequencies of up to 1300% (HER). We show that the strongly beneficial effect of aggregation arises from the favorable alignment of individual molecules, thus facilitating intermolecular charge transfer processes in the vesicles

Aggregation‐Induced Improvement of Catalytic Activity by Inner‐Aggregate Electronic Communication of Metal‐Fullerene‐Based Surfactants

A paradigm for active constituents in (homogeneous) catalysis is that optimum performance requires maximum dispersion. Generally, aggregation results in a decline. This is a different case in supramolecular catalysis. A new concept based on surfactants equipped with functional heads is presented, which becomes a more active catalyst itself upon aggregation. The head group of the surfactants is composed of a diethylenetriamine‐functionalized fullerene capable of coordinating to catalytically active metals like Co II . The improvement of catalytic properties upon aggregation is demonstrated via electrocatalytic water‐splitting reaction as a model system. Detailed electrochemistry studies were performed at concentrations below and above the critical aggregation concentration (cac). While isolated surfactant molecules represent only moderately active catalysts, drastic improvement of efficiency in the hydrogen evolution (HER) as well as in the oxygen evolution reactions (OER) were detected, once vesicular structures have formed. Self‐organization of the surfactants leads to an increase in turnover frequencies of up to 1300% (HER). The strongly beneficial effect of aggregation arises from the favorable alignment of individual molecules, thus, facilitating intermolecular charge transfer processes in the vesicles.publishe

Organometallic, Nonclassical Surfactant with Gemini Design Comprising π‑Conjugated Constituents Ready for Modification

Surfactants are functional molecules comprising a water-compatible head group and a hydrophobic tail. One of their features is the formation of self-assembled structures in contact with water, for instance, micelles, vesicles, or lyotropic liquid crystals. One way to increase the functionality of surfactants is to implement moieties containing transition-metal species. Ferrocene-based surfactants represent an excellent example because of the distinguished redox features. In most existing ferrocene-based amphiphiles, an alkyl chain is classically used as the hydrophobic tail. We report the synthesis and properties of 1-triisopropylsilylethynyl-1′-trimethylammoniummethylferrocene (FcNMe3TIPS). In FcNMe3TIPS, ferrocene is part of the head group (Gemini design) but is also attached to a (protected) π-conjugated ethynyl group. Although this architecture differs from that of classical amphiphiles and those of other ferrocene-based amphiphiles, the compound shows marked surfactant properties comparable to those of lipids, exhibiting a very low value of critical aggregation concentration in water (cac = 0.03 mM). It forms classical micelles only in a very narrow concentration range, which then convert into monolayer vesicles. Unlike classical surfactants, aggregates already form at a very low concentration, far beneath that required for the formation of a monolayer at the air–water interface. At even higher concentration, FcNMe3TIPS forms lyotropic liquid crystals, not only in contact with water, but also in a variety of organic solvents. As an additional intriguing feature, FcNMe3TIPS is amenable to a range of further modification reactions. The TIPS group is easily cleaved, and the resulting ethynyl function can be used to construct heterobimetallic platinum-ferrocene conjugates with trans-Pt(PEt3)2X (X = Cl, I) complex entities, leading to a heterobimetallic surfactant. We also found that the benzylic α-position of FcNMe3TIPS is rather reactive and that the attached ammonium group can be exchanged by other substituents (e.g., −CN), which offers additional opportunities for further functionalization. Although FcNMe3TIPS is reversibly oxidized in voltammetric and UV–vis spectroelectrochemical experiments, the high reactivity at the α-position is also responsible for the instability of the corresponding ferrocenium ion, leading to a polymerization reaction.publishe