EPR Study of Single Crystals of PROXYLs

Electron paramagnetic resonance study of the single crystals of two PROXYLs, trans-2,5-bis(4-methylphenyl)-2,5-dimethylpyrrolidine-1-oxy (±)-1] and trans-2-(4-methylphenyl)-2,5-dimethyl-5-phenylpyrrolidine-1-oxy (±)-2] was conducted. The obtained spectra were always fitted well by a single Lorentzian. The principal g-values (g _x , g _y , g _z ) of (±)-1 and (±)-2 were determined as (2.00990, 2.00639, 2.00266) and (2.01106, 2.00742, 2.00389), respectively. The profiles of half width at half maximum (HWHM) depending on two polar angles, θ and ϕ, were measured in all directions. The angular profiles of the exchange interaction (|J ₀|) were attempted to be estimated by dividing the experimental HWHM by the calculated total second moment (M ₂ ^tot) with the crystallographic data. For (±)-1, |J ₀| along the c-axis was estimated to be much larger than that along the a- or b-axis. This suggests that (±)-1 is a one-dimensional magnet along the c-axis. Authors' address: Yohei Noda, Electron Spin Chemistry Laboratory, Department of Chemistry, Graduate School of Science, Kyoto University, 606-8502 Kyoto, Japan