Metalation of tetraphenylporphyrin with nickel on a TiO2(110)-1 × 2 surface.

The in situ metalation of tetraphenylporphyrin (2HTPP) with Ni on the reconstructed TiO2(110)-1 × 2 surface, resulting in the formation of adsorbed nickel(II)-tetraphenylporphyrin (NiTPP), has been investigated by synchrotron radiation photoemission spectroscopy (SRPES), scanning tunnelling microscopy (STM) and ab initio Density Functional Theory (DFT) calculations. The metalation can be realized at room temperature irrespective of the deposition order of Ni and 2HTPP, which however leads to different metalation degrees. Increasing the substrate temperature or Ni : 2HTPP ratio results in higher metalation degree, which ultimately reaches its limit at ∼85% (Ni : 2HTPP = 3 : 1) and ∼49% (Ni : 2HTPP = 1 : 1) for post- and pre-deposition of Ni, respectively. The reaction from 2HTPP to NiTPP is accompanied by changes of the molecular adsorption conformation and the adsorption site from a tilted two-lobed feature on added Ti2O3 rows to a four-lobed feature on top of troughs or cross-links of the TiO2(110)-1 × 2 surface. This interpretation of the STM data is supported by DFT-based STM simulations.

Coordination reaction between tetraphenylporphyrin and nickel on a TiO2(110) surface.

In situ metalation of tetraphenylporphyrin (2HTPP) (sub)monolayers with Ni on a TiO2(110) surface to nickel(II)-tetraphenylporphyrin (NiTPP) depends on temperature and order of deposition, and affects conformation and bonding geometry of the porphyrin.

Surface-assisted formation, assembly, and dynamics of planar organometallic macrocycles and zigzag shaped polymer chains with C-Cu-C bonds.

The formation, structure, and dynamics of planar organometallic macrocycles (meta-terphenyl-Cu)n and zigzag-shaped one-dimensional organometallic polymers on a Cu(111) surface were studied with scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Vapor deposition of 4,4″-dibromo-meta-terphenyl (DMTP) onto Cu(111) at 300 K leads to C-Br bond scission and formation of C-Cu-C bonds, which connect neighboring meta-terphenyl fragments such that room-temperature stable macrocycles and zigzag chains are formed. The chains self-assemble to form islands, which are elongated in the direction of the chains. If DMTP is deposited onto Cu(111) held at 440 K, the island size is drastically increased (>200 × 200 nm(2)). STM sequences show the formation of ordered structures through reversible scission and reformation of the C-Cu-C bonds. The cyclic organometallic species such as the hexamer (meta-terphenyl-Cu)6 may represent intermediates in the surface-confined Ullmann synthesis of hydrocarbon macrocycles such as the recently discovered hyperbenzene.

Surface-assisted organic synthesis of hyperbenzene nanotroughs.

A hexagonal macrocycle consisting of 18 phenylene units (hyperbenzene) was synthesized on a Cu(111) surface in ultrahigh vacuum by Ullmann coupling of six 4,4''-dibromo-m-terphenyl molecules. The large diameter of 21.3 Šand the ability to assemble in arrays makes hyperbenzene an interesting candidate for a nanotrough that could enclose metallic, semiconducting, or molecular quantum dots.