Arrays of Dipolar Molecular Rotors in Tris(o-phenylenedioxy)cyclotriphosphazene

  • Ke Zhao
  • Paul I. Dron
  • Jiří Kaleta
  • Charles T. Rogers
  • Josef MichlEmail author
Part of the Topics in Current Chemistry book series (TOPCURRCHEM, volume 354)


Regular two-dimensional or three-dimensional arrays of mutually interacting dipolar molecular rotors represent a worthy synthetic objective. Their dielectric properties, including possible collective behavior, will be a sensitive function of the location of the rotors, the orientation of their axes, and the size of their dipoles. Host–guest chemistry is one possible approach to gaining fine control over these factors. We describe the progress that has been achieved in recent years using tris(o-phenylenedioxy)cyclotriphosphazene as a host and a series of rod-shaped dipolar molecular rotors as guests. Structures of both surface and bulk inclusion compounds have been established primarily by solid-state nuclear magnetic resonance (NMR) and powder X-ray diffraction (XRD) techniques. Low-temperature dielectric spectroscopy revealed rotational barriers as low as 1.5 kcal/mol, but no definitive evidence for collective behavior has been obtained so far.


Dielectric spectroscopy Hexagonal TPP Inclusion compounds Molecular rotors Powder X-ray diffraction Solid-state NMR 



(Solid-state) nuclear magnetic resonance






Density functional theory calculation with the B97-D3 functional and SVP basis set at a geometry optimized with the PM6 method






Cross-polarization with magic angle spinning




Differential scanning calorimetry








Tetra(n-butyl)ammonium chloride


Tetra(n-butyl)ammonium fluoride














Inclusion compound containing X% of guest Y in TPP as host


Powder X-ray diffraction



This material is based upon work supported in Prague by the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007–2013) ERC grant agreement no. 227756 and by the Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic RVO: 61388963, and in Boulder by the National Science Foundation under Grant No. CHE 0848663. We are grateful to Dr. Martina Čižková for taking the TEM image shown in Fig. 5.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Ke Zhao
    • 1
  • Paul I. Dron
    • 2
  • Jiří Kaleta
    • 3
  • Charles T. Rogers
    • 1
  • Josef Michl
    • 2
    • 3
    Email author
  1. 1.Department of PhysicsUniversity of ColoradoBoulderUSA
  2. 2.Department of Chemistry and BiochemistryUniversity of ColoradoBoulderUSA
  3. 3.Institute of Organic Chemistry and BiochemistryAcademy of Sciences of the Czech RepublicPrague 6Czech Republic

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