  The paper presents the Electron Paramagnetic Resonance study of defects in
the spin chain o- (DMTTF)2X family using continuous wave and pulsed techniques.
The defects in spin chains are strongly correlated and present similar
microscopic structure as a molecular magnet. By means of 2D-HYSCORE and DFT
calculations we show a strong reduction of hyperfine coupling between the
defects and the nuclear spin bath. We assume that the reduction is due to the
Heisenberg exchange interaction which screens the effect of the nuclei.
