Fritz Vögtle

Dendrimers: From Design to Application—A Progress Report

A unique combination of a clearly defined particle structure and a very highly functionalized surface is offered by the topical dendrimers. Many groups work on this unusual molecular architecture to develop new applications. The most advanced progress in this respect is an MRI contrast agent based on dendrimers (see schematic representation) that facilitate the visualization of bloodstreams.

Stimulating Concepts in Chemistry

Design and synthesis - theozymes and catalyst design organic synthesis in aqueous media domino reactions asymmetric two-center catalysis organic reactions in supercritical CO2 separation-built-in organic synthesis catalytic asymmetric synthesis of natural products combinatorial libraries architecture, organization and assembly - carbon - from fullerenes to new allotropes dendritic architecture constructive binding and slippage inclusion phenomena molecular organization molecular devices and material properties - molecular wires molecular devices and machines electron and energy transfer crystal engineering nano technology chemical sensors biological aspects - enzyme mimitics enzyme inhibitors organic synthesis and cell biology.

Host Guest Complex Chemistry III

The solvent extraction of metal ions by crown compounds.- Crown compounds as alkali and alkaline earth metal ion selective chromogenic reagents.- Photocontrol of ion extraction and ion transport by photofunctional crown ethers.- Macroheterocyclic ligands on polymers.- Synthesis and metal complexes of aza-macrocycles with pendant arms having additional ligating groups.- Bridged, capped and fenced porphyrins.

Zur nomenklatur der phane—II

Zusammenfassung Fur den neuen Begriff “PHANE” wird eine klare Definition gegeben. Ein in sich geschlossenes, sehr allgemein anwendbares und dabei doch vergleichsweise einfaches und berschaubares Nomenklatursystem fur alle Phane wird entwickelt. Die Termini “Kern”, “Brucke”, “Bruckengliederzahl” und “Ringgliederzahl” werden definiert. Zur eindeutigen Charakterisierung von Phanen mit carbocyclischem Kern sowie carbocyclischer und heterocyclischer Brucke werden die Bezeichnungen “Carbophan”, “Carba-phan” und “Hetera-phan” neu eingefuhrt. Das Prafix “hetera-” wird als allgemeiner Ausdruck und Oberbegriff fur die Silben “aza-”, “oxa-”, “thia-” usw. vorgeschlagen, die sogenannte “a-Nomenklatur” wird eindeutiger “Hetera-Nomenklatur” genannt. Die neuen Begriffe “heteralog” und “substitulog” werden erlautert. Anhand von Beispielen wird gezeigt, dass die “Phan-Nomenklatur” auch komplizierte “Metallocenophane” zwanglos zu benennen gestattet.

Structure/Chiroptics Relationships of Planar Chiral and Helical Molecules

The chiroptical properties of planar-chiral and helical molecules without stereogenic centres and with well-defined structure, strain, electronic properties and chirality are investigated by experimental and theoretical circular dichroism spectroscopy. We report on the synthetic and theoretical achievements made during the past 10 years in the field of rigid [2.2]metacyclophane propellers, as well as in the area of [n]para- and [n]metacyclophanes containing aliphatic parts like adamantane or unsaturated bridges. Results for carbo and hetero helicenes and helicene-related molecules like twisted phenanthrenes are presented. It is demonstrated how reliable theoretical calculations using configuration interaction and time-dependent methods in combination with density functional theory today are and how useful the interplay between theory and experiment stimulates the development of chiral molecules optimized for this purpose. Even for large molecules it is routinely possible to assign Cotton effects to electronic transitions, to evaluate chromophore contributions, to determine absolute configurations and conformational equilibria, and to discover intramolecular charge transfer effects.

AZOBENZENE-FUNCTIONALIZED CASCADE MOLECULES : PHOTOSWITCHABLE SUPRAMOLECULAR SYSTEMS

Potential holographic materials are obtained from the azobenzene-functionalized dendrimers described herein (shown schematically on the right). Even in the largest species presented, which contains up to 32 azobenzene chromophores, each chromophoric unit behaves independently compared to “monomer” model compounds. Diffraction efficiencies larger than 20 % were achieved with holographic films of the azobenzene dendrimers – the second-generation dendrimer exhibits good thermal stability.

HIGH-YIELDING ROTAXANE SYNTHESIS WITH AN ANION TEMPLATE

An electrophile caught like a mouse in a trap! An anionic stopper-wheel complex acts as a supramolecular nucleophile in an almost quantitative synthesis of a phenyl ether rotaxane. The electrophilic semiaxle has to thread through the macrocycle in order to contact the bulky phenolate group that is positioned on the other side, and probably tightly held in place by hydrogen bonds.

Dendrimere: vom Design zur Anwendung – ein Fortschrittsbericht

Eine einzigartige Kombination von genau definierter Partikelstruktur und sehr hoher Oberflachenfunktionalitat bieten die zur Zeit sehr aktuellen Dendrimere. Das Ziel vieler Arbeitsgruppen, die sich mit dieser ungewohnlichen Molekularchitektur beschaftigen, ist die Entwicklung neuer Anwendungen. In dieser Hinsicht am weitesten fortgeschritten ist ein Kontrastmittel auf Dendrimerbasis (siehe schematische Darstellung), das die Visualisierung von Blutbahnen ermoglicht.

Functional cascade molecules

Cascade molecules/dendrimers are highly branched, regularly built molecules that have now been known for two decades. While efforts in the early stage of their investigation were directed towards the development of higher generation structures and new dendritic architectures, the design of functional dendrimers is more and more emphasized today. The latest literature in the field reflects the search for cascade molecules that accumulate certain functional groups resulting in novel properties—the first practical applications are in sight. Dendrimers that interact with, and can be manipulated with light, appear particularly attractive and hold promises for future developments.

Fluorescent guests hosted in fluorescent dendrimers

Abstract We have investigated the formation of host–guest complexes between dendrimers of the poly(propylene amine) family functionalized with dansyl units at the periphery (hosts) with dye molecules (guests). Each dendrimer nD , where the generation number n goes from 1 to 5, comprises 2n+1 (i.e. 64 for 5D ) dansyl functions in the periphery and 2n+1−2 (i.e. 62 for 5D ) tertiary amine units in the interior. The most thoroughly investigated systems were those with eosin as a guest. The results obtained show that: (i) the nD dendrimers dissolved in dichloromethane solution extract eosin from aqueous solutions; (ii) the maximum number of eosin molecules hosted in the dendrimers increases with increasing dendrimer generation, up to a maximum of 12 for the 5D dendrimer; (iii) the fluorescence of the peripheral dansyl units of the dendrimers is completely quenched via energy transfer by the hosted eosin molecules; (iv) the fluorescence of the hosted eosin molecules is partially quenched; (v) the eosin molecules can occupy two different sites (or two families of substantially different sites) in the interior of the dendritic structure; (vi) excitation of eosin hosted in the dendrimers causes sensitization of the dioxygen emission via eosin triplet excited state. The behavior of fluorescein and rose bengal is qualitatively similar to that of eosin, whereas naphthofluorescein is not extracted. The maximum number of dye molecules extracted by the 4D dendrimer is 25 for rose bengal and ca. 1 for fluorescein, showing that the formation of host–guest species is related to the electronic properties rather than to the size of the dye molecules.