Precision Nanocluster-Based Toroidal and Supertoroidal Frameworks Using Photocycloaddition-Assisted Dynamic Covalent Chemistry

Kavalloor Murali Lakshmi, Jose V. Rival, Pakath Sreeraj, Sindhu R. Nambiar, Chinnaiah Jeyabharathi, Nonappa, Edakkattuparambil Sidharth Shibu

Research output: Contribution to journalArticleScientificpeer-review


Atomically precise nanoclusters (NCs) have recently emerged as ideal building blocks for constructing self-assembled multifunctional superstructures. The existing structures are based on various non-covalent interactions of the ligands on the NC surface, resulting in inter-NC interactions. Despite recent demonstrations on light-induced reversible self-assembly, long-range reversible self-assembly based on dynamic covalent chemistry on the NC surface has yet to be investigated. Here, it is shown that Au25 NCs containing thiolated umbelliferone (7-hydroxycoumarin) ligands allow [2+2] photocycloaddition reaction-induced self-assembly into colloidal-level toroids. The toroids upon further irradiation undergo inter-toroidal reaction resulting in macroscopic supertoroidal honey-comb frameworks. Systematic investigation using electron microscopy, atomic force microscopy (AFM), and electron tomography (ET) suggest that the NCs initially form spherical aggregates. The spherical structures further undergo fusion resulting in toroid formation. Finally, the toroids fuse into macroscopic honeycomb frameworks. As a proof-of-concept, a cross-photocycloaddition reaction between coumarin-tethered NCs and an anticancer drug (5-fluorouracil) is demonstrated as a model photo-controlled drug release system. The model system allows systematic loading and unloading of the drug during the assembly and disassembly under two different wavelengths. The results suggest that the dynamic covalent chemistry on the NC surface offers a facile route for hierarchical multifunctional frameworks and photocontrolled drug release.

Original languageEnglish
Publication statusE-pub ahead of print - 22 Jan 2023
Publication typeA1 Journal article-refereed


  • 5-fluorouracil
  • coumarin
  • drug loading
  • dynamic covalent chemistry
  • photocycloaddition
  • precision nanoclusters
  • self-assembly
  • toroidal superstructures

Publication forum classification

  • Publication forum level 3

ASJC Scopus subject areas

  • Biotechnology
  • Chemistry(all)
  • Biomaterials
  • Materials Science(all)


Dive into the research topics of 'Precision Nanocluster-Based Toroidal and Supertoroidal Frameworks Using Photocycloaddition-Assisted Dynamic Covalent Chemistry'. Together they form a unique fingerprint.

Cite this