Theoretical investigation of the β value of the phenylene and phenylene ethynylene units by evaluating exchange interaction between organic radicals

► Decay constant β of J value was calculated for different lengths of biradicals. ► For phenylene and phenylene ethynylene, β was 0.42 Å−1 and 0.24 Å−1, respectively. ► The same β was obtained for nitronyl nitroxides and verdazyls. ► The obtained βs are in good agreement with the experimental value of conductance.