Katrin Wedeking

Formation of Isomeric BAr3 Adducts of 2‐Lithio‐N‐methylimidazole

N-Methylimidazole added to the strong organometallic Lewis acid B(C6F5)3 at the donor nitrogen atom to form the adduct 3 (characterized by X-ray diffraction). Deprotonation at the imidazole carbon atom C-2 was achieved by treatment with methyllithium to generate the reactive “Arduengo carbene anion” intermediate 4, which underwent a rapid subsequent intramolecular nucleophilic aromatic substitution reaction at one of the adjacent C6F5 groups to form the tricyclic betaine-type product 5. Rearrangement of 4 by 1,2-boron migration was not observed. The respective isomer 7 was prepared independently by deprotonation of N-methylimidazole, followed by C-2 addition of B(C6F5)3. The corresponding N-methylimidazolide-2−B(C6H5)3 adduct 8 was characterized by X-ray diffraction and shown to have a cyclodimeric structure made up of intermolecular bis(π-arene)(imidazole)lithium units. A DFT study revealed that the N-borated Arduengo carbene anions are in general very effectively kinetically protected from undergoing intramolecular rearrangement to their thermodynamically favored 2-boratoimidazole anion isomers by 1,2-BR3 migration. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Surface-mounted molecular rotors with variable functional groups and rotation radii.

A strategy for designing and activating surface-mounted molecular rotors with variable rotation radii and functional groups is proposed and demonstrated. The key point of the strategy is to separate the anchor and the rotating functional group from each other by using a connector of adjustable length. The three independent parts of the molecule are responsible for different functions to support the rotating movement of the molecule as a whole. In this way, one can easily change each part to obtain molecular rotors with different sizes, anchors, and functional rotating groups.

Multilevel Supramolecular Architectures Self-Assembled on Metal Surfaces

We report the controllability of the complexity of surface-supported supramolecular assembly on metal surfaces. By introducing mismatch between the molecular packing and the surface atomic periodicity in the systems with comparable strength of intermolecular and molecule-substrate interactions, a homomolecular assembly exhibiting two-dimensional multilevel structures up to quaternary level was observed. In such a multiperiodicity modulated system, neither the intermolecular nor molecule-substrate interactions solely dominate the assembly, resulting in complicated multilevel structures. We further demonstrated that the multilevel assemblies can serve as templates for site-selective adsorption of guest molecules.