Fig. 4: Head-to-tail coupling of 1 on Ag(111) held at 520 K.
From: Polycyclic aromatic chains on metals and insulating layers by repetitive [3+2] cycloadditions
a Overview STM image after deposition of 1 onto a Ag(111) substrate held at 520 K shows polymerization towards one-dimensional molecular chains. (b) STM and (c) bond-resolved AFM image of a pentamer recorded with a CO-functionalized tip shows formation of imidazole rings between the monomer units—analogous to the coupling observed on Au(111). Red arrows highlight brightly imaged phenyl rings bending upwards due to steric repulsion. The terminal cyano group of the pentamer shown in b and c is cleaved off. Such loss of –CN has repeatedly been observed on Ag(111). Scan parameters: (a), (b) VS = 100 mV, I = 10 pA, (c) VS = 0 V, AOSC = 80 pm, constant height. Frequency shift range: (c) −4.5 to 1.0 Hz.
