Controlled polymerization and self-assembly of halogen-bridged diruthenium complexes in organic media and their dielectrophoretic alignment

Rempei Kuwahara, Shigenori Fujikawa, Keita Kuroiwa, Nobuo Kimizuka

Research output: Contribution to journalArticle

19 Citations (Scopus)


Lipophilic paddlewheel biruthenium complexes [Ru 2(μ-O 2CR) 3X] n (O 2CR = 3,4,5-tridodecyloxybenzoate, X = Cl, I) self-assemble in organic media to form halogen-bridged coordination polymers. The polymerization is accompanied by spectral changes in π(RuO,Ru 2) → π*(Ru 2) and π(axial ligand) → π*(Ru 2) absorption bands. These polymeric complexes form lyotropic liquid crystals in n-decane at concentrations above ∼100 unit mM. The bridging halogen axial ligands (X = Cl or I) exert significant influences on their electronic structures and self-assembling characteristics: the chloride-bridged polymers give hexagonally aligned ordered columnar structure (columnar hexagonal phase, Col h), whereas the iodide-bridged polymers form less ordered columnar nematic (Col n) phase, as revealed by small-angle X-ray diffraction measurements. Chloro-bridged coordination polymers dispersed in n-decane are thermally intact even at the elevated temperature of 70 °C. In contrast, iodo-bridged polymers show reversible dissociation and reassembly phenomena depending on temperature. These halogen-bridged coordination polymers show unidirectional alignment upon applying alternating current (ac) electric field as investigated by crossed polarizing optical microscopy and scanning electron microscopy. The unidirectionally oriented columns of chloro-bridged polymers are accumulated upon repetitive application of the ac voltage, whereas iodo-bridged coordination polymers show faster and reversible alignment changes in response to turning on-and-off the electric field. The controlled self-assembly of electronically conjugated linear complexes provide a potential platform to design electric field-responsive nanomaterials.

Original languageEnglish
Pages (from-to)1192-1199
Number of pages8
JournalJournal of the American Chemical Society
Issue number2
Publication statusPublished - Jan 18 2012

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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