We further aimed to understand the physical and chemical origins of the conductance behavior of ladder-type molecules. We first determined the single-crystal structures of L1-PF6 and N1-PF6 (Figs. ) by X-ray diffraction. The molecular backbone of non-ladder molecule N1-PF6 showed a large dihedral angle of 69.8° between phenyl and isoquinolinium moieties due to its non-ladder structure. Conversely, L1-PF6 with shape-persistent ladder backbone exhibited a significantly smaller dihedral angle of 31.8°. DFT calculations revealed that in L1-PF6, both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) span the entire molecule. This electronic configuration creates a seamless, unhindered pathway for electron transport while simultaneously constraining the backbone flexibility (Fig. ). On the other hand, the HOMO and LUMO of the N1-PF6 were localized on opposite ends of the rotatable C-N bond (Fig. ). These apparent differences in the electronic and structural properties results in drastic differences in the single-molecule electronic properties for these two types of molecules.