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

Journal Article · Wed Oct 08 04:00:00 EDT 2014 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja508119d· OSTI ID:1171258

Olankitwanit, Arnon ^[1]; Pink, Maren ^[2]; Rajca, Suchada ^[1]; Rajca, Andrzej ^[1]

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1. Univ. of Nebraska, Lincoln, NE (United States)
2. Indiana Univ., Bloomington, IN (United States)

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 ΔE_ST 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 ΔE_ST (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 ΔE_ST applicable to moderately pure diradicals in matrices.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: NSF
• OSTI ID: 1171258
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 40 Vol. 136; ISSN 0002-7863
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: ENGLISH