Characterization of one-dimensional molecular chains of 4,4′-biphenyl diisocyanide on Au(111) by scanning tunneling microscopy

Abstract

The morphology and electronic structure of vapor deposited 4,4'-biphenyldiisocyanide (BPDI) on a Au(111) surface were investigated using variable-temperature scanning tunneling microscopy. When deposited at room temperature, BPDI molecules form one-dimensional molecular chains similar to that recently observed for the structurally related 1,4-phenyl diisocyanide (PDI). Compared to PDI, the longer periodicity for the BPDI molecular chains is consistent with the addition of a second phenyl ring and supports a structural model in which the BPDI molecules lie parallel to the surface and interconnected by Au-adatoms. The molecular chains are mostly aligned along the 11̄0 direction of the Au(111) substrate, but exhibit frequent changes in angle that are consistent with directions between fcc and hcp three-fold hollow sites. Dispersion-corrected density functional theory calculations for one-dimensional chains of BPDI molecules bound end-to-end via their isocyanide groups to Au-adatoms reproduce the observed periodicity of the chains and show that this morphology is energetically favored over upright binding with one free -NC group. The spatially resolved conductance (dI/dV) map for BPDI on Au(111) exhibits a feature centered at -0.67 eV below the Fermi level which are delocalized along the chain with maxima at the Au-adatom and biphenyl positions. This occupied resonant feature is close to that previously observed for the PDI in both photoemission and conductance measurements and is attributed to an occupied interfacial state resulting from BPDI-Au interactions.

Iodine versus Bromine Functionalization for Bottom-Up Graphene Nanoribbon Growth: Role of Diffusion

“…Both species preferentially adsorb along the herringbone reconstruction and aggregate into islands as the coverage increases. No evidence is seen for the removal of atoms from the metal substrate. − A noticeable difference between islands of precursors 1 and 2 is that the brominated monomers (precursor 2 ) appear to be less disordered than those formed by the iodinated monomers (precursor 1 ). This difference is even more striking after annealing the sample to 50 °C as shown in Figure c,d.…”

Adsorption and Oligomerization of 1,3-Phenylene Diisocyanide on Au(111)

“…17 Nevertheless, 4,4′-biphenyl diisocyanide does form oligomeric assemblies on Au(111), implying that rigid, longer-chain diisocyanides can self-assemble to form conducting oligomers. 18 Thus, by analogy to 1,4-BDT, 1,3-phenylene diisocyanide (1,3-PDI) should be capable of forming oligomers that incorporate gold adatoms when adsorbed on Au(111), and should show a zigzag pattern as a consequence of the nonlinear isocyanide dihedral angle. The experimental results described below demonstrate that this is the case.…”

On‐Surface Assembly of Au‐Dicyanoanthracene Coordination Structures on Au(111)

“…Au has an atomic number of 79, making it one of the heaviest of the metal atoms; it possesses a strong spin-orbit coupling and hence, presents an interesting option for metalorganic networks. Au has been found to form two-fold coordination with alkanethiolate [25,26], phenylthiolate [27], pyridyl [20,22], isocyano [28][29][30][31][32], and cyano groups [33,34]. Three-fold coordination has been reported with the cyano [33,35] and pyridyl groups [22].…”