On-surface synthesis approach to preparing one-dimensional organometallic and poly-p-phenylene chains

Abstract

On-surface Ullmann coupling reactions of dibromo-biphenyl and diiodo-biphenyl molecules on Ag(111), Cu(111), Au(111) and Au(100) and by deposited extrinsic Ag and Ni atoms were systematically explored. Poly-p-phenylene polymer chains turned out to be the final coupling products. Different organometallic polymer chains, [–Ph₂Ag–]_n, [–Ph₂Cu–]_n, and [–Ph₂Ni–]_n, were synthesized as stable intermediates during the coupling reactions. These intermediates were confirmed and verified by X-ray photoelectronic spectroscopy, scanning tunnelling spectroscopy and tip manipulations. On Au surfaces, coupling products were achieved directly from halogenated precursors without formation of the Au-containing organometallic intermediates. Magnetic organometallic polymer chains were prepared by Ullmann coupling of dibromo-biphenyl activated by extrinsic Ni atoms on Au(100) surface and were confirmed by Kondo resonance measurement. Such an on-surface preparation strategy may provide an efficient approach to preparing unentangled organometallic and pure organic polymer chains and subsequently measuring their properties at surfaces.