Fast Oxidative Cyclooligomerization towards Low- and High-Symmetry Thiophene Macrocycles

Macrocycles with quaterthiophene subunits were obtained by cyclooligomerization by direct oxidative coupling of unsubstituted dithiophene moieties. The rings were closed with high selectivity by an α,β'-connection of the thiophenes as proven by NMR spectroscopy. The reaction of the precursor with terthiophene moieties yielded the symmetric α,α'-linked macrocycle in low yield together with various differently connected isomers. Blocking of the β-position of the half-rings yielded selectively the α,α'-linked macrocycle. Selected cyclothiophenes were investigated by scanning tunneling microscopy, which displayed the formation of highly ordered 2D crystalline monolayers.