Electron nuclear double resonance of S= 1/2 defects in a single crystal of the morpholinium–TCNQ 1 : 1 complex

Abstract

Single crystals of the morpholinium–TCNQ 1 : 1 complex give e.s.r. spectra showing a central resonance at g= 2 in addition to the lines of thermally excited triplet excitons. ENDOR spectra recorded by saturating the central line show that it is due to isolated TCNQ anions which are produced at two different crystal defects. The hyperfine tensors of the TCNQ anion obtained from ENDOR give a spin density distribution in the solid much different from that in solution. The polarization of the spin distribution is consistent with a rearrangement of the morpholinium cations around the anion in the defect.