Fig. 6.

Bond-order analyses. a, c Constant-height AFM images of IF taken with CO tip at V = 0 V on Cu(111) (Δz = −2.1 Å) (a) and on 2 ML NaCl (Δz = 1.5 Å) (c). b, d To emphasise the structure of the molecule, Laplace-filtered AFM images are also shown. e, f Bond orders of IF in its open-shell (e) and closed-shell (f) resonance structures. The s-indacene moiety is highlighted in green (f). On the bond-order scale, 0 refers to a single bond and 1 to a double-bond⁴⁵. Bond orders were determined by using the bond lengths of relaxed geometries. Scale bars, 500 pm