Seven synthetic ferrocenylnaphthalene diimide derivatives (FNDs) interact with tetraplex DNA. Two of the FNDs had the highest affinity for tetraplex DNA with 106 M− 1 order of binding. Three of the FNDs inhibit telomerase activity without inhibiting Taq polymerase. A different three FNDs inhibit both telomerase and Taq polymerase. One of the FNDs didn't inhibit either telomerase or Taq polymerase.