Extended Data Fig. 2: Electronic structure of the molecular products obtained via sequential probe-assisted cyclodehydrogenation.
From: Intelligent synthesis of magnetic nanographenes via chemist-intuited atomic robotic probe
(a) Spin-polarized DFT calculations of molecular orbital diagrams of freestanding molecule 1 and molecule 3. (b) dI/dV spectra acquired at the edge of molecule 1 and 3 with the reference spectra collected over the bare Au(111) surface. dI/dV spectrum collected at the zigzag edge of molecule 1 shows two pronounced peaks located at −1.25 V (±0.05 V) and +1.46 V (±0.05 V), respectively (Upper curve). Similarly, dI/dV spectrum collected at the edges of molecule 3 after a second cyclization shows two small peaks (Middle curve) located at −0.54 V (±0.05 V) and +1.12 V (±0.05 V). As illustrated in Extended Data Fig. 2a, the frontier orbitals of a neutral molecule 1 contain two degenerate singly occupied molecular orbitals (ψ5↑ and ψ6↑, denoted as SOMOs) at −0.52 eV below EF and two singly unoccupied molecular orbitals (ψ5↓ and ψ6↓), denoted as SUMOs) at +1.47 eV above EF, in line with the experimental energetic position of occupied (−1.25 V) and unoccupied (+1.46 V) electronic states. Similarly, a neutral molecule 3 is predicted to have two pairs of frontier orbitals assigned to the SOMOs (ψ5↑ and ψ6↑, −0.47 eV) and SUMOs (ψ5↓ and ψ6↓, +1.11 eV), consistent with the experimentally recorded electronic states at −0.54 V and +1.12 V, respectively (Extended Data Fig. 2a, right). (c) Point dI/dV spectra acquired over different sites (indicated by coloured circles in the STM images shown on the right) of molecule 1–4 on Au(111) surface. Scale bar: 5 Å.
