Cyclodehydrogenation reactions of TNTP-tBu 1a on Cu(110). (a–c) STM overview images that were
obtained after the evaporation of 1a (a), and after annealing
the sample at 590 K (b) and at 620 K (c). (d–f) STM zoomed-in
images of an initial TNTP-tBu molecule, a typical
intermediate molecule and a final product molecule, respectively.
(g–i) Constant-height frequency shift AFM images of the three
molecules shown in (d–f); (j–k) corresponding chemical
structures. Imaging parameters: (a–e) 0.1 V, 10 pA; (f) 10
mV, 100 pA; and tip heights Z = +50 pm (g), +130
pm (h), and +120 pm (i) (Z = −120 pm for the
region between the two red dashed lines in (i)), where the ±
signs represent the increase/decrease of the tip–sample distance
relative to the STM set point (0.1 V, 10 pA) on the adjacent Cu(110)
surfaces. Since the contrast in (i) is separately optimized for the
middle section and the top/bottom sections, an overall color bar is
not given.