Figure 2.

Oligomer containing monomer 2 subunits. (a) nc-AFM image of an oligomer chain on Au(111) (T = 4 K; tip height corresponds to tunnel current set point V_s = 50 mV and I = 30 pA above Au(111)). (b) Schematic representation of chemical structure of the oligomer in a. Arrows indicate short (red) and long (green) bonds between indenyl groups. The dashed box shows monomer structure 2. (c) DFT calculated bond lengths for a four-unit oligomer chain (composed of units of 2 as seen in b) as a function of the location of the bond along the chain. Red and green dots indicate short and long bonds between indenyl groups, while blue dots indicate bonds within the five-membered rings (calculation shown for an oligomer chain having unsaturated radical valences at the chain ends; results are similar for hydrogen-terminated chains).