Aiming at the transfer of molecular processes from solution to solid supports, metal-ion mediated layer-by-layer self-assembly strategies are applied. For this purpose, terpyridine and pyridine functionalized Hunter/Vögtle-type tetralactam macrocycles and rotaxanes are deposited into ordered multilayer-arrays on gold substrates.
The novel benzo-21-crown-7-substituted bis(urea) low-molecular weight gelator can hierarchically assemble into helical fibrils, which further develop into bundles and finally form a stable gel in acetonitrile. The gel–sol transition can be controlled by three different molecular recognition events: K+ binding to the crown ethers, pseudorotaxane formation with secondary ammonium ions and Cl- binding to the urea units. With the gelator, and these chemical stimuli, a number of different systems can be designed that behave as logic gates. Depending on the choice of components, OR, AND, XOR, NOT, NOR, XNOR and INHIBIT gates have been realized. Thus, the gel–sol transition as a property of the system as a whole is influenced in a complex manner.
The knowledge about self-organization, template effects and multivalency allows a more easy and effective synthesis of multithreaded rotaxanes and catenanes. Multivalent host and guest systems can be used to evaluate systematically their thermodynamic and kinetic properties.
The studied multivalent systems possess different binding motifs (crown ethers/ammonium and tetralactammacrocycles/several guests) and can be built up following different strategies. New homo- and heterovalent crown-ammonium pseudorotaxanes can provide supramolecular systems for useful studies of their complex formation behavior.
One of our studies highlights the spacer-length and flexibility affect on the thermodynamic stabilities and assembly kinetics of noncovalently bonded pseudorotaxanes formed by divalent crown ethers and secondary ammonium axles. The ammonium functionalities are separated by spacers of different lengths, which show clear trends. In addition, the rarely observed effect of chelate cooperativity in a pseudorotaxane was supported by a crystallographic structure, which was obtained with the help of our close cooperation partner K. Rissanen et. al. in Finland. The chelate cooperativity was quantified by Isothermal Titration Calorimetry and double mutant cycle analyses.
Analytical characterization, structural studies, comparison of reactivity in the condensed and the gas phase for example of hydrogen-bonded capsules, metallosupramolecular helicates, polygons, and polyhedra, or intertwined molecules such as rotaxanes, catenanes and knots
ESI mass spectrometry associated with infrared multi-photon dissociation (IRMPD) tandem MS experiments is used to confirm the formation of the large and quite stable metal oxido cluster and perform gasphasereactions. Aggregation- and Ligandexchange are done by microreactor reactions in the second time-scale.
Purity, dispersity, and defect analysis, fragmentation mechanisms, differentiation of structural isomers, host-guest chemistry of dendrons and dendrimers including POPAM, Fréchet-type and persulfonylated dendrimers as well as dendritic self-assembled metallosupramolecular squares.
Templated synthesis and functionalization of interlocked molecules, deslipping kinetics of rotaxanes for the evaluation of the steric size complementarity of the wheel's cavity and the stopper size, controlled molecular movements in molecular devices
Formation and ligand exchange mechanisms, thermodynamic and kinetic properties, cages with converging functional groups, dynamic combinatorial libraries
Gas-phase studies on anion recognition, C-H/anion interactions, anion/pi interactions