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Title: Synthesis of Aza-m-Xylylene diradicals with large singlet-triplet energy gap and statistical analyses of their EPR spectra

We describe synthesis and characterization of a derivative of aza-m-xylylene, diradical 2, that is persistent in solution at room temperature with the half-life measured in minutes (~80–250 s) and in which the triplet ground state is below the lowest singlet state by >10 kcal mol⁻¹. The triplet ground states and ΔEST of 2 in glassy solvent matrix are determined by a new approach based on statistical analyses of their EPR spectra. Characterization and analysis of the analogous diradical 1 are carried out for comparison. Statistical analyses of their EPR spectra reliably provide improved lower bounds for ΔEST (from >0.4 to >0.6 kcal mol⁻¹) and are compatible with a wide range of relative contents of diradical vs monoradical, including samples in which the diradical and monoradical are minor and major components, respectively. This demonstrates a new powerful method for the determination of the triplet ground states and ΔEST applicable to moderately pure diradicals in matrices.
 [1] ;  [2] ;  [1] ;  [1]
  1. Univ. of Nebraska, Lincoln, NE (United States)
  2. Indiana Univ., Bloomington, IN (United States)
Publication Date:
OSTI Identifier:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 136; Journal Issue: 40
American Chemical Society (ACS)
Research Org:
Argonne National Laboratory (ANL), Argonne, IL (United States)
Sponsoring Org:
Country of Publication:
United States