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

Publikation: Beitrag in FachzeitschriftArtikelForschungPeer-Review

Autorschaft

  • Stefan Bitter
  • Marius Kunkel
  • Lisa Burkart
  • André Mang
  • Rainer F. Winter
  • Sebastian Polarz

Externe Organisationen

  • Universität Konstanz
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Details

OriginalspracheEnglisch
Seiten (von - bis)8854-8864
Seitenumfang11
FachzeitschriftACS Omega
Jahrgang3
Ausgabenummer8
Frühes Online-Datum9 Aug. 2018
PublikationsstatusVeröffentlicht - 31 Aug. 2018
Extern publiziertJa

Abstract

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 (FcNMe 3TIPS). In FcNMe 3TIPS, 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, FcNMe 3TIPS forms lyotropic liquid crystals, not only in contact with water, but also in a variety of organic solvents. As an additional intriguing feature, FcNMe 3TIPS 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(PEt 3) 2X (X = Cl, I) complex entities, leading to a heterobimetallic surfactant. We also found that the benzylic α-position of FcNMe 3TIPS 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 FcNMe 3TIPS 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.

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Organometallic, Nonclassical Surfactant with Gemini Design Comprising π-Conjugated Constituents Ready for Modification. / Bitter, Stefan; Kunkel, Marius; Burkart, Lisa et al.
in: ACS Omega, Jahrgang 3, Nr. 8, 31.08.2018, S. 8854-8864.

Publikation: Beitrag in FachzeitschriftArtikelForschungPeer-Review

Bitter, S, Kunkel, M, Burkart, L, Mang, A, Winter, RF & Polarz, S 2018, 'Organometallic, Nonclassical Surfactant with Gemini Design Comprising π-Conjugated Constituents Ready for Modification', ACS Omega, Jg. 3, Nr. 8, S. 8854-8864. https://doi.org/10.1021/acsomega.8b01405
Bitter, S., Kunkel, M., Burkart, L., Mang, A., Winter, R. F., & Polarz, S. (2018). Organometallic, Nonclassical Surfactant with Gemini Design Comprising π-Conjugated Constituents Ready for Modification. ACS Omega, 3(8), 8854-8864. https://doi.org/10.1021/acsomega.8b01405
Bitter S, Kunkel M, Burkart L, Mang A, Winter RF, Polarz S. Organometallic, Nonclassical Surfactant with Gemini Design Comprising π-Conjugated Constituents Ready for Modification. ACS Omega. 2018 Aug 31;3(8):8854-8864. Epub 2018 Aug 9. doi: 10.1021/acsomega.8b01405
Bitter, Stefan ; Kunkel, Marius ; Burkart, Lisa et al. / Organometallic, Nonclassical Surfactant with Gemini Design Comprising π-Conjugated Constituents Ready for Modification. in: ACS Omega. 2018 ; Jahrgang 3, Nr. 8. S. 8854-8864.
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abstract = "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 (FcNMe 3TIPS). In FcNMe 3TIPS, 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, FcNMe 3TIPS forms lyotropic liquid crystals, not only in contact with water, but also in a variety of organic solvents. As an additional intriguing feature, FcNMe 3TIPS 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(PEt 3) 2X (X = Cl, I) complex entities, leading to a heterobimetallic surfactant. We also found that the benzylic α-position of FcNMe 3TIPS 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 FcNMe 3TIPS 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. ",
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T1 - Organometallic, Nonclassical Surfactant with Gemini Design Comprising π-Conjugated Constituents Ready for Modification

AU - Bitter, Stefan

AU - Kunkel, Marius

AU - Burkart, Lisa

AU - Mang, André

AU - Winter, Rainer F.

AU - Polarz, Sebastian

N1 - Funding Information: Funding The current research was funded by an ERC consolidator grant (I-SURF; project 614606). Notes The authors declare no competing financial interest.

PY - 2018/8/31

Y1 - 2018/8/31

N2 - 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 (FcNMe 3TIPS). In FcNMe 3TIPS, 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, FcNMe 3TIPS forms lyotropic liquid crystals, not only in contact with water, but also in a variety of organic solvents. As an additional intriguing feature, FcNMe 3TIPS 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(PEt 3) 2X (X = Cl, I) complex entities, leading to a heterobimetallic surfactant. We also found that the benzylic α-position of FcNMe 3TIPS 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 FcNMe 3TIPS 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.

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