The electrical, electrochemical, and optical properties of new ambient air stable conducting polymers, prepared by complexation of ladder poly(benzobisimidazobenzophenanthroline) (BBL) and its semiladder analogue BBB with poly(styrenesulfonic acid), are reported. The transition from insulator ( < 10(-12) S/cm) to electronic conductor (2 S/cm) occurs when neutral BBL or BBB is about 70-100 mol % singly protonated. This transition is accompanied by a large shift of the formal reduction potential from -0.85 and -0.69 V for neutral BBL and BBB to 0.35 and 0.33 V versus SCE, respectively, for the protonated conducting forms. Although the HOMO-LUMO optical band gap remains unchanged at 1.8 eV, the electron affinity (LUMO level) estimated from cyclic voltammetry was found to shift from 4.2 and 4.5 eV in the neutral BBL and BBB to 5.3 and 5.4 eV, respectively, in the protonated conducting polymers. Thus, contrary to previous thought the electronic structures of this conjugated ladder polymer and its semi-ladder analogue undergo a large change upon protonic acid doping. The stability and unusually large electron affinity of the conducting BBL/PSSA and BBB/PSSA complexes make them attractive as electron injection/collection layers in polymer-based optoelectronic devices.