Scanning tunneling micrographs of ordered layers of two thiophene-alkylpyrrole oligomers on graphite

Scanning tunneling micrographs of two linear oligomers with six and seven units of thiophene (S) and N-dodecylpyrrole (P12) arranged as SP12SSP12S (molecule 1) and SP12SP12SP12S (molecule 2) dissolved in phenyloctane, and imaged on a highly oriented pyrolytic graphite with a Pt/Ir tip, show ordered rows (lines) of oligomers. Molecule 1 has a single packing structure, an interline repeat distance of 19±0.5إ perpendicular to the bright lines (aromatic rings) and dark regions (dodecyl tails), and an intraline distance of 8±0.3 إ. Molecule 2 shows three domains with subtly different molecular ordering, with repeat distances of 23±0.5 إ (interline) and 18±0.5 إ (intraline). For both molecules the aromatic rings may lie almost in the graphite plane.