Fig. 4: Energy-resolved analysis for single chain.

a Scanning tunneling spectroscopy (STS, black curve) and inelastic electron tunneling spectroscopy (IETS, gray curve) of single molecule of 2. The STS plot reveals an increasing electronic state around \(\pm \)800 mV, with a peak observed around zero energy. The inset displays the STS with a smaller voltage range with the corresponding IETS. The red shadow region marks the peak around −19 mV. Two signals in IETS indicate two vibrational modes, the stretching mode of C-C bonds at 135 meV and C = C bonds at 185 meV. More statistical data about STS and IETS are shown in Supplementary Fig. 9 and Supplementary Table 3. b The calculated projected density of states (DOS) of diphenyl [n] conjugated polyene sandwiched between two copper electrodes. It presents a pinned frontier orbital around zero energy for various molecular lengths. The purple arrow, orange arrow and brown arrow assign three peaks of a diphenyl [20] conjugated polyene molecule with specific molecular orbitals, which is similar for other molecules. c A schematic diagram of two vibrational modes of a diphenyl [20] conjugated polyene molecule in the calculation model. d Illustration of Fermi-level pinning formed at the molecular-electrode interface in this case. Blue and bronze regions mark the occupation of electron in molecular orbitals and copper electrode. Source data are provided as a Source Data file.