Now showing 1 - 5 of 5
  • Publication
    Circularly polarized lanthanide luminescence from Langmuir-Blodgett films formed from optically active and amphiphilic Eu(III) based self-assembly complexes
    The development of novel chiral amphiphilic self-assembled complexes 13Eu and 23Eu by using Europium(III) directed synthesis is described. These systems form stable Langmuir films at an air-water interface, which were transferred onto solid supports (quartz slides) resulting in stable monolayers that exhibit time delayed Eu(III) centered emission and circular polarized luminescence (CPL) upon excitation of the chiral naphthyl antennae.
      729Scopus© Citations 79
  • Publication
    The Potential of N-Heterocyclic Carbene Complexes as Components for Electronically Active Materials
    (Swiss Chemical Society, 2010-03) ; ;
    The application of N-heterocyclic carbene complexes as active sites in materials other than catalysis has been remarkably scarce. Inspired by the — often misleading — ‘carbene’ label, which implies a substantial degree of M=C π bonding, we have been interested in evaluating the potential of N-heterocylclic carbene complexes as building blocks for constructing electronically active materials. Electron mobility via the metal-carbon bond has been investigated in monometallic imidazol-2-ylidene complexes and subsequently expanded to polymetallic systems. In particular, ditopic benzobisimidazolium-derived ligands have been explored for the fabrication of bimetallic molecular switches and main-chain conjugated organometallic polymers. Electrochemical analyses have allowed for quantifying the degree of electronic coupling between the metal sites and for identifying the key parameters that govern the intermetallic communication.
      693Scopus© Citations 35
  • Publication
    Probing Intermetallic Coupling in Dinuclear N-Heterocyclic Carbene Ruthenium(II) Complexes
    A series of bimetallic N-heterocyclic carbene (NHC) ruthenium(II) complexes were synthesized, which comprise two [RuCl2(cymene)(NHC)] units that are interlinked via the NHC nitrogens by alkyl chains of different length. Electrochemical characterization revealed two mutually dependent oxidation processes for the complex with a methylene linker, indicating moderate intramolecular electronic coupling of the two metal centers (class II system). The degree of coupling decreases rapidly upon increasing the number of CH2 units in the linker and provides essentially decoupled class I species when propylene or butylene linkers are used. Electrochemical analyses combined with structural investigations suggest a through-bond electronic coupling. Replacement of the alkyl linker with a p-phenylene group afforded cyclometalated complexes, which were considerably less stable. The electronic coupling in the methylene-linked complex and the relatively robust NHC–ruthenium bond may provide access to species that are switchable on the molecular scale.
      363Scopus© Citations 48
  • Publication
    Main-chain organometallic polymers comprising redox-active iron(II) centers connected by ditopic N-heterocyclic carbenes
    Main-chain organometallic polymers were synthesized from bimetallic iron(II)complexes containing a ditopic N-heterocyclic carbene (NHC) ligand [(cp)(CO)LFe(NHC~NHC)Fe (cp)(CO)L]X2 (where NHC~NHC represents a bridging dicarbene ligand, L = I– or CO). Addition of a diimine ligand such as pyrazine or 4,4’-bipyridine interconnected these bimetallic complexes and gave the corresponding co-polymers containing iron centers that are alternately linked by a dicarbene and a diimine ligand. Diimine coordination was depending on the wingtip groups at the carbene ligands and was accomplished either by photolytic activation of a carbonyl ligand from the cationic [Fe(cp)(NHC)(CO)2]+ precursor (alkyl wingtips) or by AgBF4-mediated halide abstraction from the neutral complex [FeI(cp)(NHC)(CO)] (mesityl wingtips). Remarkably, the polymeric materials were substantially more stable than the related bimetallic model complexes. Electrochemical analyses indicated metal-metal interactions in the pyrazine-containing polymers, whereas in 4,4’-bipyridine-linked systems the metal centers were electronically decoupled.
      829Scopus© Citations 74
  • Publication
    Beyond catalysis: N-heterocyclic carbene complexes as components for medicinal, luminescent, and functional materials applications
    (RSC Publishing, 2010) ;
    This tutorial review compiles the advances that have been achieved in using transition metal complexes containing N-heterocyclic carbene ligands as components for materials. Applications of metal carbene complexes in fields different from catalysis are remarkably scarce. During the last few years, promising results have been accomplished in particular by utilizing such complexes as antimicrobial and cytotoxic agents, as photoactive sites in luminescent materials, for self-assembly into liquid crystalline materials and metallasupramolecular structures, and as synthons for molecular switches and conducting polymeric materials. These initial achievements clearly underline the great potential of N-heterocyclic carbene complexes in various fields of materials science.
      2471Scopus© Citations 649