Formation of Highly Luminescent Supramolecular Architectures Possessing Columnar Order from Octupolar Oxadiazole Derivatives: Hierarchical Self-Assembly from Nanospheres to Fibrous Gels

Authors

  • Shinto Varghese,

    1. Photosciences and Photonics Section Chemical Sciences and Technology Division National Institute for Interdisciplinary Science and Technology, CSIR Trivandrum, 695 019 (India)
    Search for more papers by this author
  • Nambalan S. Saleesh Kumar,

    1. Photosciences and Photonics Section Chemical Sciences and Technology Division National Institute for Interdisciplinary Science and Technology, CSIR Trivandrum, 695 019 (India)
    Search for more papers by this author
  • Anjali Krishna,

    1. Photosciences and Photonics Section Chemical Sciences and Technology Division National Institute for Interdisciplinary Science and Technology, CSIR Trivandrum, 695 019 (India)
    Search for more papers by this author
  • Doddamane S. Shankar Rao,

    1. Centre for Liquid Crystal Research, Jalahalli Bangalore, 560 013 (India)
    Search for more papers by this author
  • Subbarao Krishna Prasad,

    1. Centre for Liquid Crystal Research, Jalahalli Bangalore, 560 013 (India)
    Search for more papers by this author
  • Suresh Das

    Corresponding author
    1. Photosciences and Photonics Section Chemical Sciences and Technology Division National Institute for Interdisciplinary Science and Technology, CSIR Trivandrum, 695 019 (India)
    • Photosciences and Photonics Section Chemical Sciences and Technology Division National Institute for Interdisciplinary Science and Technology, CSIR Trivandrum, 695 019 (India).
    Search for more papers by this author

  • Dedicated to Professor C. N. R. Rao on the occasion of his 75th birthday

Abstract

The synthesis and study of the liquid crystalline, photophysical, and aggregation behavior of novel octupolar oxadiazole derivatives are reported. These molecules formed columnar mesophases at elevated temperatures which transformed into a glassy state at ambient temperatures wherein the columnar order was retained. Their spontaneous concentration dependent hierarchical self-assembly from spheres to fibrous gels has been investigated using TEM, SEM, and XRD. Retention of the hexagonal columnar (Colh) order was also observed in the fibrous aggregates. Concentration dependent luminescence spectral studies indicated that the change in morphology from spheres to fibrous aggregates was associated with a shift in chromophore packing from predominantly H-type to J-type aggregates. Time resolved anisotropic investigations revealed that the columnar stacking of molecules in the aggregated state provided a pathway for excitation energy migration to the lower energy J-traps.

Ancillary