Engineering topics
Siemeling, U
Publications and source records attributed to Siemeling, U.
Phthalocyaninato Complexes with Peripheral Alkylthio Chains: Disk-like Adsorbate Species for the Vertical Anchoring of Ligands onto Gold Surfaces
Thin metalorganic films were prepared on gold by self-assembly of thioether-functionalized phthalocyaninato complexes from solution. The phthalocyaninato ligands used contain eight peripheral, {beta}-positioned, alkylthio substituents SR (1a: R = n-C{sub 8}H{sub 1}7, 1b: R = n-C{sub 12}H{sub 25}), which serve as headgroups for surface binding and promote lateral assembly, while the disk-like phthalocyaninato core offers the scope for the attachment of axial ligands to the adsorbed molecules. This process was mimicked by coordination of pyridine (Py) to [Zn(1a)] and [Zn(1b)], respectively. The crystal structures of the products [Zn(1a)(Py)] and [Zn(1b)(Py)] were determined. The crystal structures of 4,5-bis(octylthio)phthalodinitrile and 4,5-bis(dodecylthio)phthalodinitrile were also determined. The films fabricated from [Mn(1a)Cl] and [Mn(1b)Cl] on gold were characterized by XPS, ToF-SIMS and NEXAFS spectroscopy, which revealed the presence of well-defined and homogeneous self-assembled monolayers (SAMs), whose constituents are bound to the substrate by thioether-gold linkages. The orientation of the macrocycles is predominantly parallel to the surface. Strong electronic interaction of the manganese(III) centre with the substrate leads to Cl loss upon adsorption and its reduction to MnII.
NHC-based Self-assembled Monolayers on Solid Gold Substrates
Thin films of 1,3-diethylbenzimidazol-2-ylidene (BIEt) were fabricated from THF solution on solid gold substrates and characterised by high-resolution X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopy. The surface-analytical data are in accord with the formation of self-assembled monolayers of BIEt molecules exhibiting an approximately vertical orientation on the substrate. The crystal structure of (BIEt){sub 2} was also determined.