Triplet excitons in the simple tetracyanoquinodimethane (TCNQ) salts ${\mathrm{Rb}}^{+}$${\mathrm{TCNQ}}^{-}$ and ${\mathrm{}\left(\mathrm{trimethylbenzimidazolium}\right)\mathrm{}}^{+}$${\mathrm{TCNQ}}^{-}$

The experimental dipolar splitting tensors of the triplet excitons and their contribution to the magnetic susceptibility are reported for two TCNQ (tetracyanoquinodimethane) salts, i.e., ${\mathrm{Rb}}^{+}$ ${\mathrm{TCNQ}}^{-}$ and trimethylbenzimidazolium ${\mathrm{TCNQ}}^{-}$. An exciton model intermediate between the localized and the free-electron limit is presented. Application of this model shows that the usual Heisenberg antiferromagnet treatment of these semiconducting TCNQ salts is not valid.