Crossover from a Solid Effect to Thermal Mixing 1H Dynamic Nuclear Polarization with Trityl-OX063

Asif Equbal, Yuanxin Li, Tarnuma Tabassum, Songi Han

Research output: Contribution to journalArticlepeer-review


Trityl-OX063 is a narrow-line, water-soluble, and biocompatible polarizing agent, widely used for dynamic nuclear polarization (DNP) amplified NMR of 13C, but not of the abundant 1H nuclear spin, for which the ineffective solid effect (SE) is expected to be operational. Surprisingly, we observed a crossover from SE to thermal mixing (TM) DNP of 1H with increasing Trityl-OX063 concentration at 7 T. We experimentally ascertained diagnostic signatures of TM-DNP that have only been theoretically predicted: (i) an electron paramagnetic resonance (EPR) spectrum that maintains an asymmetrically broadened EPR line from strong e-e couplings and (ii) hyperpolarization, i.e., cooling of select electron-spin populations, manifested in a characteristic pump-probe electron double-resonance spectrum under DNP conditions. Low microwave power requirements, high polarization transfer rates, and efficient DNP at high magnetic fields are the key benefits of TM-DNP.

Original languageEnglish (US)
Pages (from-to)3718-3723
Number of pages6
JournalJournal of Physical Chemistry Letters
Issue number9
StatePublished - May 7 2020

ASJC Scopus subject areas

  • General Materials Science
  • Physical and Theoretical Chemistry


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