Multi Electron Spin Cluster Enabled Dynamic Nuclear Polarization with Sulfonated BDPA

Celeste Tobar, Kaitlin Albanese, Raj Chaklashiya, Asif Equbal, Craig Hawker, Songi Han

Research output: Contribution to journalArticlepeer-review


Dynamic nuclear polarization (DNP) can amplify the solid-state nuclear magnetic resonance (NMR) signal by several orders of magnitude. The mechanism of DNP utilizing α,γ-bisdiphenylene-β-phenylallyl (BDPA) variants as Polarizing Agents (PA) has been the subject of lively discussions on account of their remarkable DNP efficiency with low demand for microwave power. We propose that electron spin clustering of sulfonated BDPA is responsible for its DNP performance, as revealed by the temperature-dependent shape of the central DNP profile and strong electron-electron (e-e) crosstalk seen by Electron Double Resonance. We demonstrate that a multielectron spin cluster can be modeled with three coupled spins, where electron J (exchange) coupling between one of the e-e pairs matching the NMR Larmor frequency induces the experimentally observed absorptive central DNP profile, and the electron T1e modulated by temperature and magic-angle spinning alters the shape between an absorptive and dispersive feature. Understanding the microscopic origin is key to designing new PAs to harness the microwave-power-efficient DNP effect observed with BDPA variants.

Original languageEnglish (US)
Pages (from-to)11640-11650
Number of pages11
JournalJournal of Physical Chemistry Letters
Issue number51
StatePublished - Dec 28 2023

ASJC Scopus subject areas

  • General Materials Science
  • Physical and Theoretical Chemistry


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