Ag/Ag + ), and the profile is almost identical with that of BMP, except a slight positive shift (Figure ). This suggests that the two redox-active carbonyl pyridinium units in 1 remain completely independent, which is in line with related systems. Compared with 1, each pair of reduction waves in 2 is split into two, leading to the appearance of four reversible reduction waves, with the reduction potentials (vs. Ag/Ag + ) determined to be E1/2(1) = -0.97 V, E1/2(2) = -1.07 V, E1/2(3) = -1.60 V and E1/2(4) = -1.72 V. The reason could again be attributed to the intramolecular charge transfer due to the introduction of stronger electron-donating bithiophene linker. The peak-to-peak separation (ΔEp-p) for each wave is ca. 60 mV, indicating their good reversibility. In Figure , the differential pulse voltammograms (DPV) further confirm the four-electron reduction processes of 1 and 2, and the patterns are consistent with the CV. The CV of 3 is almost identical with that of 2 (Figure ). In addition, a negligible loss of signal is observed in both cases after 10 continuous CV cycles at a scan rate of 100 mV/s, suggesting their excellent electrochemical stability. Overall, each carbonyl pyridinium unit can serve as two-electron storage unit. As such, compounds 1 and 2 can store up to four electrons per molecule. To make it more intuitive, the four-electron transfer processes are depicted in Figure . The first two-electron reduction event leads to the formation of neutral radical species, and the second two-electron reduction produces the formation of anionic species, in line with the electrochemical data for BMP reported in the literature. In dilute DMF solution, the π to π* absorption peak maximum of 2 is located at max= 402 nm, which is 80 nm red-shifted compared to 1 at max = 322 nm (Figure ). Moreover, 2 exhibits an additional low-energy absorption shoulder at 525 nm, which is attributed to intramolecular charge transfer from electron-donating bithiophene to carbonylpyridinium units. From the onset of the absorption (1: onset= 375 nm; 2: onset= 600 nm), a narrower energy band gap (Eg = 2.07 eV) is determined for 2 compared to 1 (Eg = 3.31 eV). Based on the equation ELUMO = -[𝐸 𝑜𝑛𝑠𝑒𝑡 𝑟𝑒𝑑 -E(Fc/Fc + ) + 4.8] eV, the lowest unoccupied molecular orbital (LUMO) energies were calculated to be -3.8 eV for both 1 and 2. While the same LUMO energy level means that both compounds have identical electron affinity, the narrow band gap for 2 indicates its high electron conductivity, which is confirmed by the conductivity measurement.