Winter, Rainer F.
Four different emissions from a Pt(Bodipy)(PEt3)2(S-Pyrene) dyad
2019-01-22, Irmler, Peter, Gogesch, Franciska S., Larsen, Christopher B., Wenger, Oliver S., Winter, Rainer F.
The Pt(bodipy)-(mercaptopyrene) dyad BPtSPyr shows four different emissions: intense near-infrared phosphorescence (Φph up to 15%) from a charge-transfer state pyrS˙+-Pt-BDP˙−, additional fluorescence and phosphorescence emissions from the 1ππ* and 3ππ* states of the bodipy ligand at r.t., and phosphorescence from the pyrene 3ππ* and the bodipy 3ππ* states in a glassy matrix at 77 K.
Organometallic, Nonclassical Surfactant with Gemini Design Comprising π-Conjugated Constituents Ready for Modification
2018-08-31, Bitter, Stefan, Kunkel, Marius, Burkart, Lisa, Mang, André, Winter, Rainer F., Polarz, Sebastian
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.
Redox-Rich Metallocene Tetrazene Complexes : Synthesis, Structure, Electrochemistry, and Catalysis
2019-03-25, Vanicek, Stefan, Jochriem, Markus, Hassenrück, Christopher, Roy, Souvik, Kopacka, Holger, Wurst, Klaus, Müller, Thomas, Winter, Rainer F., Reisner, Erwin, Bildstein, Benno
Thermal or photochemical metal-centered cycloaddition reactions of azidocobaltocenium hexafluoridophosphate or azidoferrocene with (cyclooctadiene)(cyclopentadienyl)cobalt(I) afforded the first metallocenyl-substituted tetrazene cyclopentadienyl cobalt complexes together with azocobaltocenium or azoferrocene as side products. The trimetallic CpCo compounds are highly conjugated, colored, and redox-active metallo-aromatic compounds, as shown by their spectroscopic, structural, and electrochemical properties. The CpCo-tetrazenido complex with two terminally appended cobaltocene units catalyzes electrochemical proton reduction from acetic acid at a mild overpotential (0.35 V). Replacing cobaltocene with ferrocene moieties rendered the complex inactive toward catalysis.
Metallo‐Scorpionates : First Generation of Trimetallic, Homoleptic [Ru]–M–[Ru] Complexes (M = Fe, Co, Ni, Cu)
2018-11-01, Schlapp-Hackl, Inge, Hassenrück, Christopher, Wurst, Klaus, Kopacka, Holger, Müller, Thomas, Winter, Rainer F., Bildstein, Benno
The first metallo‐scorpionate ligands, closely related to Trofimenko's scorpionates, are obtained by formal replacement of the hydrido‐boron moiety of hydrido‐tris(pyrazolyl)borate by an (arene)RuII fragment. Coordination to divalent and trivalent 3d‐transition metals (Fe, Co, Ni, Cu) gives access to a series of homoleptic, heterotrimetallic complexes containing linear metal chains bridged by pyrazole ligands. Synthetic aspects, spectroscopic, structural and electrochemical properties are reported and compared to those of standard scorpionate complexes.
Tetrakis[3,5-bis(pentafluorosulfanyl)phenyl]borate : A Weakly Coordinating Anion Probed in Polymerization Catalysis
2019-07-22, Langford, Daniel, Göttker-Schnetmann, Inigo, Wimmer, Florian P., Casper, Larissa A., Kenyon, Philip, Winter, Rainer F., Mecking, Stefan
Tetraruthenium Metallamacrocycles with Potentially Coordinating Appended Functionalities
2018-09, Anders, Patrick, Rapp, Mario Robin, Linseis, Michael, Winter, Rainer F.
We present four new tetraruthenium macrocycles built from two 1,4-divinylphenylene diruthenium and two isophthalic acid building blocks with peripheral, potentially mono- or tridentate donor functions attached to the isophthalic linkers. These macrocycles are characterized by multinuclear NMR spectroscopy, mass spectrometry and, in the case of the thioacetyl-appended complex 4, by X-ray crystallography. Cyclic and square wave voltammetry establish that the macrocycles can be oxidized in four consecutive redox steps that come as two pairs of two closely spaced one-electron waves. Spectroscopic changes observed during IR and UV/Vis/NIR spectroelectrochemical experiments (NIR = near infrared) show that the isophthalate linkers insulate the electroactive divinylphenylene diruthenium moieties against each other. The macrocycles exhibit nevertheless pronounced polyelectrochromism with highly intense absorptions in the Vis (2+/4+ states) and the NIR (2+ states) with extinction coefficients of up to >100,000 M−1·cm−1. The strong absorptivity enhancement with respect to the individual divinylphenylene diruthenium building blocks is attributed to conformational restrictions imposed by the macrocycle backbone. Moreover, the di- and tetracations of these macrocycles are paramagnetic as revealed by EPR spectroscopy.