Spontaneous separation of on-surface synthesized tris-helicenes into two-dimensional homochiral domains.

The on-surface Ullmann coupling of 2,3-dibromo[4]helicene molecules is studied on Au(111) and Cu(111) surfaces. Bis-helicene and tris-helicene are identified with scanning tunnelling microscopy and X-ray photoelectron spectroscopy as reaction products. The produced star-shaped tris-helicenes self-assemble on Au(111) spontaneously into large homochiral domains.