Nanoscale assemblies of gigantic molecular {Mo154}-rings: (Dimethyldioctadecylammonium)20[Mo154O462H 8(H2O)70]

Tomoyuki Akutagawa, Reina Jin, Ryo Tunashima, Shin Ichiro Noro, Leroy Cronin, Takayoshi Nakamura

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)

Abstract

Clusters based on the mixed-valence gigantic inorganic ring [Mo 154O462H14(H2O)70] 14- ({Mo154}-ring) and dimethyldioctadecylammonium (DODA) were combined to form novel molecular assemblies of an inorganic-organic hybrid molecular system as Langmuir-Blodgett (LB) and cast films. (DODA) 20[Mo154O462H8(H2O) 70] (2) was prepared by cation exchange and was characterized by a combination of thermogravimetry, IR, UV-vis-NIR, 1H NMR, and XRD measurements. The salt 2 was soluble in common organic solvents, and the chemical stability of {Mo154}-ring encapsulated by DODA cationic surfactants in CHCl3 was found to be higher than that of the "native" sodium salt of the {Mo154}-ring in H2O. Uniform spherical vesicle-like molecular assemblies of (DODA) 20[Mo154O462H8(H2O) 70] were observed in dilute THF, whose average diameter of 95 nm and a normalized variance of 5.7% were confirmed by a X-ray small-angle scattering. Deposition of 2 as a cast film showed circular domains with a typical diameter of ∼100 nm, indicating possible similarities between solution and surface-deposited structures. The resulting LB films of salt 2 were transferred from an acidic buffer subphase with pH = 1.5 onto mica, giving a two-dimensional film surface with a unity transfer ratio. Further, the electronic absorption spectra of the LB multilayer were consistent with the classic type II mixed-valence MoV/MoVI electronic state well know for molybdenum blue {Mo154}-ring systems, and it appears that on the surface the plane of the {Mo154}-ring is approximately parallel to the substrate surface, as indicated by polarized electronic spectra, while the alkyl chains of DODA were relatively normal to the substrate surface. Therefore, the layer between the {Mo154}-rings and DODA cations was alternately stacked along the direction of film propagation. Finally, it was found that the surface morphology of the cast and LB films was determined by the molecular assembly of (DODA)20[Mo154O462H 8(H2O)70] in solution and the air-water interface, respectively.

Original languageEnglish
Pages (from-to)231-238
Number of pages8
JournalLangmuir
Volume24
Issue number1
DOIs
Publication statusPublished - 2008 Jan 1
Externally publishedYes

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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