Formation of polyphenyl chains through hierarchical reactions: Ullmann coupling followed by cross-dehydrogenative coupling.

From an interplay of UHV-STM imaging and DFT calculations, we have illustrated on-surface formation of polyphenyl chains through a hierarchical reaction pathway involving two different kinds of reactions (Ullmann coupling and cross-dehydrogenative coupling), which will provide a deeper understanding of on-surface chemical reactions and an alternative and efficient strategy to fabricate desired surface molecular nanostructures.